The vast majority of scholarly history work is done in archives. There are archives that cover just about everything you could imagine. Government archives for official records, institutional archives (like of a company) that cover the history of the insitution, church archives for various religions or individual churches, private archives that cover an individual who may or may not be famous to the average person, and archives which cover any range of topics. For your purposes, there are diary archives. I don't study American or British history, so I'm not familiar with English language archives as much, but in my specialty of Northwest Europe, there is the Nederlandse Dagboekarchief and the Deutsches Tagebucharchiv.

You're likely to find two severe limitations in searching for what you're looking for.

1. You're looking for stuff that's been digitized. Don't get me wrong, a lot of stuff has been digitized, but even more has not. Generally speaking, archives do not get the best funding in the world, and when it comes to preserving documents versus digitizing them, they will work with preserving the original every time.

2. You're looking for stuff in English. That is, for the most part, going to limit you to stuff that has been translated or stuff that was originally written in English. Translation costs money, so it's rarely done unless its for publication. Publication costs money as well, so that means you generally have to pay for access (usually through buying a book or subscribing to a database).

That all being said, there are some online repositories that contain ego-documents of the type you're looking for.

• The Internet History Sourcebooks Project has a large collection of primary sources available for free. Most of it has been translated into English.
• California State University San Marcos has a list of online archives covering various topics.
• The Liberty, Equality, Fraternity archive at GMU has put a lot of translated stuff from the French Revolution online.
• Yale University's Avalon Project contains primary documents relating to law and diplomacy.
• The United States Holocaust Memorial Museum has a good chunk of stuff available online, although it's only a fraction of their total collection.
• The National Archives and Records Administration has some stuff online, as does the Library of Congress. I've never looked, but I'd imagine you can get some stuff from the British Library as well.

This is just scratching the surface really. If you narrow down your search criteria (i.e. more narrow than "journal style" from the "distant past"), I'd bet someone here can point you in the right direction.

Have fun!

edit: words

I know we're not supposed to roll this way on AH, but hopefully it's okay here because this is a methodology question...

Google-fu is your friend.

"Journal archives", "journal collections," and "diary archives" turned up a bunch of academic journals and modern blogs. But a search for "diary collections" was quite fruitful. "Historical diaries" suggested (you know, the "Searches related to" at the bottom of each Google page) I try "historical diaries online" which also worked well.

Google Books is finnicky, but it can be very helpful. In your case, I'd go to GB, search for "diary", and then narrow down the search options to "Free Google eBooks." Why? Because that limits your search results to (a) what you can read online and (b) "historical" diaries (thanks, copyright). You can also narrow it down further by year of publication. I definitely recommended putting on the "Free ebooks" filter, though, to avoid frustration.

Does that sound too frustrating and hit-or-miss? Unfortunately it can be, especially at the beginning. But that's, well, historical research. And as you can imagine from /u/Jan_van_Bergen's post, Google is much more efficient than archival research! (Especially when your archives are across an ocean, hehe.) You get used to it--you learn the rhythms of what to search for (like how I had success with diary and not journal), what kinds of titles university digital archives give to their websites, how to tango with Google Books and archive.org.

Also, if you have a specific time period or geographic area in mind, it never hurts to ask someone who knows the source body for that area. Like, "diaries" as you're envisioning weren't really a genre in medieval Europe, but a medievalist could direct you to some sets of sources--more likely in print, but possibly online--that would let you access at least some of what you're looking for in that type of source.

Finally, if you'd be interested in eavesdropping on a letter collection rich in daily life and emotions details instead of requiring a journal specifically, might I direct you to my new obsession: Elisabeth-Charlotte von der Pfalz, Duchesse d'Orleans at the court of Louis XIV. One of the volumes of her letters translated into English is online, and it's...fantastic.

Cardinal de Richelieu, in spite of all his ability, used to have violent attacks of madness. Sometimes he would imagine that he was a horse, and would gallop round the billiard table, striking out at his servants with his feet, neighing and making a shocking noise for about an hour, after which his people used to put him to bed, and cover him up well, when he would go to sleep and sweat profusely. When he awoke he would remember nothing of what had happened.

and

I am sorry to hear that you have become addicted to coffee. Nothing in the world is more unhealthy...The Princesse de Hanau, daughter of Duke Christian de Birkenfelt, died of it after horrible suffering. It was found after her death that the coffee had caused hundred of little ulcers in her stomach.

Let that be a lesson to you.

So, we have archival sources, which Jan_van_Bergen explained. Then we have digitized archival sources, which Sunagainstgold explained. The third most common sources would be BOOKS!

But not just any book. What youre looking for is called primary sources, documents, reports, journals, and other records created by an actor, their proxy, or somebody living contemporaneously. Some of these sources, and especially diaries and memoirs, get reprinted for modern consumption. Sitting all in a line next to me, I have the memoirs of US Grant, WT Sherman, and James Longstreet. Then a few books down are the letters and dispatches of Robert E. Lee. These books are either the direct written testimony of the people, in the case of the memoirs, or a collection of published letters and documents, in the case of Robert E Lee. These books exist for many of the world's most famous people, from Julius Caesar to Hillary Clinton. They also range in style from piece of propaganda (Like Ceasar's works, or, arguably, Clinton's most recent memoir) to honest examinations of famous events, like Grant's memoir, to collections of letters. My father, for example, loves Civil War letter collections and diaries, and owns several books like that.

To find these sources, Amazon is your best friend. As is Google Books (which is also free!). They can tell you just as much as archival sources in some cases, and are designed for human consumption.