Say I'm a farmer in 1791 France and the revolution happens - how much would my life have changed by the end of the revolution?

This is a massive question that can be aptly summed up as "It depends."

Where do you reside? Most specifically, are you from the North or the South? Another question I need to ask is how old are you? What gender are you? Those last two are the most important because, frankly, they determine how likely it is that you live or die. How rich are you, your family? Do you have any royal ties whatsoever? If the answer is yes to the last line this post ends here because you were near guaranteed to be dead flat out as long as you stayed in France.

Let's say you were from the South. The South of France experienced a disproportionately large amount of anti-Revolutionary tendencies and would be considered in "semi-revolt" throughout the 1790's. Mayors were extra corrupt and outright ignored calls for conscription. If you were not old enough to be conscripted (unlikely, you'd have to be in your late 30's, 40's, or 50's by this point along with some kind of medical issue to really seal the deal) you would likely be victim at some point or another of a Revolutionary Army -- sans-culottes. This would be initially paraded by our friend Maximillien Robespierre -- the architect of what is called "The Terror" between '92 and '93. Almost 3/4th's of those killed in 'The Terror' would be people just like you -- regular working class peasants accused of hoarding grain or anti-revolutionary thought. Frankly, these bands were filled with people who felt it safer and more profitable to wage war on defenseless French civilians than to go out and defend the country. It was full of cowards and, I know this is loaded language, terrorists.

You would be visited by these sans-culottes regularly and would see either a family member or a friend in town sent to the guillotine most certainly. You may also have witnessed or fallen victim to noyades -- mass drownings -- or mass shootings if your town was deemed as harboring anti-Revolutionary sentiment. Thankfully though if you would survive this period through about 1794 the Terror would end with Robespierre's fall and the rise of the Directory which would dismantle these Revolutionary Armies and scatter them throughout the regular army. Let me reiterate this -- whether you are in the North or South, if you were not in the military, you were subject to seemingly random and completely unregulated murder by Revolutionary forces in the first few years of the revolution. Your chances of surviving this if you had any aristocratic heritage, any anti-revolutionary sentiment or hoarded any food whatsoever was not very high.

If you were in the North you would experience a life very similar to the South except with slightly less Revolutionary Terror and more death and destruction from war. The North would be subject to constant attacks by the British and Austrians in particular. Remember at this time the area of the Low Countries was held by Austrian nobility and would be a staging area for Austrian offensives into France. Whether it was a British, Austrian, or French army your farm would likely be destroyed entirely. Burned to the ground most likely and all your crops stolen by foraging parties and your soil destroyed by men constantly marching through and fires. I'd also wager it's likely if you have any daughters they would be raped if you were in an area of particular contention.

Basically if you were not drafting into the military your likely options were death, destruction of everything you own, rape and murder of your family, and your town or province being irrevocably destroyed by war or paramilitary Revolutionary forces. It is highly unlikely you would escaped unscathed.

What is far more likely (and far more interesting to talk about) however is that you were drafted into the military. All men between the ages of 18 and 25 were to be forcibly conscripted for military service -- all men. Men into their 30's would also regularly volunteer or be called upon as well though. If you were fighting your first few years in the military would be one of utter disorganization and panic. Revolutionary hype would be ripe and you and your comrades would feel it. Any officers living a little too luxuriously? Mob them and send them to the guillotine. Your NCO being a little too harsh on you and your mates? That doesn't sound like liberty or fraternity, I don't like being drilled! You'd probably be part of a mob that killed him or stripped him of his power. It is very likely you would be witness or a participant in the murder of an individual whose only crime was being a bit rich, an aristocratic heritage, or was being a bit too strict with you.

Where you fought doesn't really matter, your life would be hell. Supply issues were rampant as the Royal Armies rather sophisticated supply system would be sacked entirely for being part of the old system. A new administrative service would be created which had a semi-independent status, its commissaires-ordonnateurs only responsible to the Republic itself and not the commanders it served. These men, responsible for collecting, storing, preparing, and issuing foodstuffs and clothing along with disbursing money were filled with endless opportunities of larceny. Supplies and cash would frequently vanish before reaching the troops going into the pockets of Revolutionary leaders in Paris. Vincentius Zahn, a pastor in Hinterzarten, watched a French army pass through in 1796 which would be about when the supply issue began to stabilize. So this is the best case scenario you're about to read:

One did not see [compared to the Austrian army] so many wagons or so much baggage, such elegant cavalry, or any infantry officers on horseback below the grade of major. [Austrian infantry lieutenants had their own mounts] Everything about these Frenchman was supple and light -- movements, clothing, arms, and baggage, In their ranks marched boys of fourteen and fifteen; the greater part of their infantry was without uniforms, shoes, money, and apparently lacking all organization, if one were to judge by appearances alone. . . These French resembled a savage horde [but] they kept good order, only some marauders who followed the army at a distance . . . terrified the inhabitants.

You had no shoes most certainly. The Directory in '95 had to pass a special order just to give all the Officers their own shoes and even that wasn't filled out entirely. Your uniform was nonexistent as is mentioned but just a loose collection of tattered blue or white with the French tricolor somewhere on it if you could manage. You had no regular supply of food from the country itself but had to survive off of war. Most early campaigns you would fight in would not be explicit offensives but 'liberating' nearby towns across the Rhine or in North Italy for supplies. Soldiers had no issue foraging on their own French lands as well. If you were a conscript you would most likely abandon your men while marching through familiar land. Many Divisions would lose half their men on extended marches through attrition and desertion alone.

Artillery and cavalry was restricted mostly to pre-war soldiers who had the training and knowledge to perform those duties. If you were conscripted you were almost certainly put into one of two areas -- light infantry or regular infantry. Tirailleur and Fusilier respectively. Assuming you did not desert after being thrown into one of these two sections you would get two very separate combat experiences. The post-Revolutionary army was very fond of skirmisher forces for some inexplicable reason. I say that mainly because inexperienced troops are very poor skirmishers. They generally aren't crack shots and flee at the slightest sign of trouble. Yet whole battalions were frequently deployed as entirely skirmishers, a tactic dubbed "tirailleur en grandes bandes." If you were part of a skirmisher force you would likely not be thrown directly into the fray. You would be sent on small scale raiding 'missions' with a small number of other skirmisher comrades and an officer as a sort of training exercise. You would raid storage caches or small villages so that you would get used to being under fire in a more controlled environment for your officer to control you. As you would go into battle against a formal Austrian, British, Italian or Prussian army your duty would be constant harassment.

If you were thrown into the fusiliers you would be heavily drilled about formation. The common trope about Napoleonic warfare are two sides standing in line formation staring each other down 50-100 yards apart and shooting at each other. This is a shitty strategy for the French, pardon my French. Line formation is inefficient for untrained conscripts because, like a phalanx, it requires holding formation and firing in concert -- two things conscripts will not be capable of doing on a few weeks of training under heavy fire. The French military doctrine of this time was one of constant attack -- always being on the offensive. It was the only way they would abuse their manpower advantage. You would be organized into a column of just a few men wide and dozens of men deep. You likely would not fire your weapon once or just once in a battle, as you were charging at full sprint into the enemy line. That is what the column provided -- it gave depth to the line, did not require a lot of organization, and was only used as a formality to charge into shattered and notably thin lines of the enemy. British, Austrian, Italian and Prussian troops were professional armies and would fight in that line formation. It would not stand up to constant column charges.

How would a normal battle go? Well, again, it depended on your position in the army. Again you were most certainly in the infantry if you were just a farmer. Let's imagine it from the enemies shoes. Swarms of skirmishers would begin to envelop your tight, strictly dressed formations firing from cover in completely disorderly formations. When I say swarm, we're talking 3:1 ratios here. If you stand still, you will be continuously picked off. If you try to fire on them, you will only hit a few as they were extremely scattered. If you tried to charge them they would drift away, still shooting, and follow you when you try to fall back into your strictly disciplined line.

Eventually your line would be in tatters you, a Brit or Austrian alike, would look up across the horizon. Out of the smoke comes a howling, trampling, massive rush of thousands of men with bayonets extended with the weight of 12 men against every yard of your exhausted line (which were only 3 deep when it all began). Your professional, organized, and chivalrous armies would try their best but they would keep running into issues. A French NCO who was completely outnumbered and outmaneuvered that just failed to recognize his hopeless situation and charged anyway, killing thousands in a last stand. Inexperienced French officers who would show a shocking disregard of accepted military strategy and turn every engagement into a mindless, all out slugfest where fancy tactics and strategy of the non-Revolutionary sides meant nothing and would buckle under the weight of thousands of Frenchmen bearing down on them.

Back to the French perspective. Let's say, somehow, you survive all of this. It's not unreasonable, many did. You did not get poked with a bayonet or shot in a charge or desert your men or didn't get caught hoarding anything. You survived the '90's into 1799 when the Directory would fall. A hundred battles would harrow you. You would time and time again throw the English and Austrians back in particular. What many tens of thousands died of combat many more would die of your governments incompetence. The patriotic enthusiasm you held in '91 seemed immature and stupid to the ragged veterans of 1799. The bands would play the patriotic airs of those first years of revolution -- Chant du Départ, Ah ça Ira, and the Marseillaise.

The bands would play and you would sing, but they would mean nothing to you. You were a professional soldier in a professional army now. You, who fought out of pride and comradeship in '91 had spent the last decade learning to loot and murder to survive and would hold little reverence for any person or any idea and especially for that damn Revolution. Your Generals would be a wolf-breed, disrespectful of authority and independent minded. All of you, officers and men together, were survivors. Men of steel, toughened to all the hardship and conditions of the worst wars in history up to that point, thoroughly fed up with the gros-ventres -- big bellies -- of the Revolutionary government in Paris who had used and abused you. You had won dozens of victories and thrown the entirety of Europe onto its backfoot but you had no peace, no shoes, and not a square meal in nearly 10 years. It was this army that would make Napoleon Bonaparte First Consul at the beginning of the 19th century. And this army was comprised of you, dangerous metal which would be forged into the Grand Armée -- the greatest military force the world would ever see.

Notes:

Elting, John, Swords Around a Throne: Napoleon's Grande Armée