I am unsure if this is what you're looking for exactly. Heinz Guderian, in his second book, Panzer Leader (originally Erinnerungen eines Soldaten in German) recounts much of his experiences and thoughts during the war. Here are some excerpts that you may find relevant:

When I was compelled to assume the duties of Chief of the General Staff, on July 21st, 1944, the situation on the Eastern Front was far from satisfactory...

...If the picture here was bad, the situation on Army Group Centre's front had become catastrophic since June 22nd and, indeed, could scarcely have been worse. The Russians attacking between the Beresina and the Pripet had succeeded, during the period June 22nd to July 3rd, in breaking through the German front in the areas Rogachev, Chaussy, north of Orsha and on both sides of Vitebsk; after totally destroying twenty-five German divisions they had forced the army group back to a line Davidgrodek-Baranowicze-Molodeczno-Koziany-the Dvina north of Polotsk. During the course of the next few days the Russians forcefully exploited their surprisingly great success, captured Pinsk and reached a line Pruzana-Volkovisk-the Niemen east of Grodno-Kovno-the Dvina east of Dunaburg-Idriza. Thus not only Army Group Centre but also Army Group North was involved in the general collapse.

On January 25th I met the German Foreign Minister in his newly built and splendid official residence on the Wilhelmstrasse. I did not mince my words with Herr von Ribbentrop. Apparently he had not realised the gravity of the situation and he asked, anxiously, if what I had told him was the exact truth: „The General Staff seems to me to be losing its nerve.‟ As a matter of fact a man needed an almost cast-iron nervous system to carry out these exploratory conversations with the requisite calm and clear consideration. After my detailed exposition I asked the „architect of Germany's foreign policy‟ if he was ready to accompany me to see Hitler and to propose to him that we attempt to secure an armistice at least on one front. I was thinking primarily of an armistice in the West. Herr von Ribbentrop replied in these words: „I can't do it. I am a loyal follower of the Fuhrer. I know for a fact that he does not wish to open any diplomatic negotiations with the enemy, and I therefore cannot address him in the manner you propose.‟ I then asked: „How would you feel if in three or four weeks time the Russians were to be at the gates of Berlin?‟ With every mark of horror Ribbentrop cried: „Do you believe that that is even possible?‟ When I assured him that it was not only possible but, as a result of our actual leadership, certain, for a moment he lost his composure. Yet when I repeated my request that he accompany me to see Hitler he did not dare agree. All I managed to get out of him was a remark made just as I was leaving: „Listen, we will keep this conversation to ourselves, won't we?‟ I assured him that I should do so.

...So my attempt to work with the Foreign Minister in an attempt to arrange an armistice on at least one front was a failure....

...I was therefore determined not to be discouraged by Herr von Ribbentrop's refusal to act, but to try the same plan through other channels. During the first week of February I approached one of the most important men in Germany with this end in view, but my proposal was turned down in exactly the same words as those which Ribbentrop had used. A third attempt I made in March will be described later.

By January 27th the Russian tidal wave was rapidly assuming, for us, the proportions of a complete disaster...

On March 21st, in accordance with the decision taken by Dr. Barandon and myself, I went to see Himmler with the purpose of urging him that he use his official contacts in neutral countries to arrange for an armistice. I found him in the Chancellery garden, taking a stroll with Hitler among the rubble. Hitler saw me and called out, asking what it was I wanted. I replied that I was desirous of talking with Himmler. So Hitler walked away and I had the National SS Leader to myself. I told him bluntly what he had already known for a long time: „The war can no longer be won. The only problem now is how most quickly to put an end to the senseless slaughter and bombing. Apart from Ribbentrop you are the only man who still possesses contacts in neutral countries. Since the Foreign Minister has proved reluctant to propose to Hitler that negotiations be begun, I must ask you to make use of your contacts and to go with me to Hitler and urge him that he arrange an armistice.‟ Himmler replied: „My dear Colonel-General, it is still too early for that.‟ I said: „I don't understand you. It is not now five minutes to twelve but five minutes past twelve. If we don't negotiate now we shall never be able to do so at all. Don't you realise how pitiful our situation has become?‟ Our conversation continued in this inconclusive vein for some time, but without result. There was nothing to be done with the man. He was afraid of Hitler.

...Speer composed a new memorandum which began unambiguously enough: “The war is lost.” He gave it to me to read before submitting it to Hitler. Unfortunately there was no contradicting it. Hitler read the first sentence and then locked it away in his safe along with all the other warnings he had received. During these tragic days I was present on one occasion when, after the evening briefing, Speer requested that Hitler receive him. Hitler refused to see him, remarking: „All he wants is to tell me again that the war is lost and that I should bring it to an end.‟ Speer refused to be fobbed off in this way and once again sent the adjutant in to Hitler with the memorandum. Hitler said to the young SS officer: „Put the document in my safe.‟ Then he turned to me and said: „Now you can understand why it is that I refuse to see anyone alone any more. Any man who asks to talk to me alone always does so because he has something unpleasant to say to me. I can't bear that.‟

Just for clarification, are you asking about an officer "realizing" that Germany would not win the war?

Follow up question, didnt Rommell express doubts about the german prospects of victory in North Africa and got sent to France instead?

I recommend reading up Ian Kershaw's "The End". It goes into great detail as to why officers kept going even if they knew everything had ended (or why they didn't believe that it's all over already).

Keep in mind that any memoirs written by any Wehrmacht General or Field Marshal should be taken with a grain of salt as they likely wrote what they did to make themselves and/or their friends look better.

That being said, General Balck, who was one of the generals compared in Freeman Dyson's (yes, the physicist, and I"m not sure why) Weapons and Hope, recently had his memoirs published in English. In his memoirs, which he claims are taken directly from his journal entries from 1914-1945, he notes after speaking with Guderian in November 1941:

"On 30 November I reported to Brauchitsch and gave him a rather blunt assessment of the condition of the force. A sick, broken man sat in front of me, but he assessed the situation much as I did. Hitler, meanwhile, was demanding more and more attacks, because he believed that the last battalion thrown into the battle would determine the outcome. Thus, the piecemeal dribbling would continue, not resulting in anything. Brauchitsch, who normally was self-controlled, broke down, "Why don't you go and tell him yourself? We are finished."

I was deeply shaken. Napoleon had tried to do something similar at Eylau (now Bagrationovsk) in 1807, and the instrument broke in his hands. The only viable course of action was to suspend the operation and transition to the defensive..."

However, he subsequently notes after the winter that there may be hope in the Spring. It is likely due to the changing strategic situation that affects the overall morale and thus view of the war situation.

Absolutely. I highly recommend reading "The Rommel Papers" edited by B.H. Liddell-Hart. It's a collection of General Rommel's own journals and maps interspersed with letters to his wife and the commentary of his second in command, General Bayerlein, and his son Manfred.

It's clear from Rommel's personal diaries that he understood Germany to be losing the war at least two years before the German Surrender. Rommel was an extraordinary example of the consummately professional soldier who consistently adhered to the German high command's strategic goals, despite their frequently unrealistic ideas of the nature of warfare. His personal diaries detail how far this disagreement went. While he maintained determination, it's clear that he saw little to no chance of success for the German army in North Africa after the First Battle of El Alamein. Once the remainder of the army was captured before they could evacuate the continent, he was fairly matter of fact that he believed the war effort to have been lost.

Yeah, near the end the Germans started to realize they were fucked. I read about an old German joke about air forces, which went "if it's the British, we duck. If it's the Americans, everybody ducks. If it's the Luftwaffe, nobody ducks."