Yesterday evening, I mistyped my GPG passphrase a couple of times. I wasn't very worried back then and didn't try further, after all I was at a pub before and had one or two beers.
Today, I wasn't able to correctly type my GPG passphrase, either. At this point, I got a slight panic. I don't have my GPG passphrase written down anywhere, didn't make up any mnemonics for it and I wouldn't be able to easily write it down anyway - it just flowed naturally through my fingers until today. In fact, I couldn't even tell how many characters/digits there are exactly. Maybe once or twice a month I would make a typo, but always get it right on second attempt. And now, from one day to the other, my fingers just couldn't remember anymore.
I literally tried hundreds of times, with different characters and character combinations, but once I started thinking about what my passphrase might be, I couldn't just type it in sub-consciously anymore. After a while I became really worried - are these the first signs of Alzheimer or something? I even tried doing something else for a while as a distraction and then suddently jumping back at the keyboard, hoping the magic would return into my fingers when they got taken by surprise.
A couple of hours and countless retries later, I suddently typed in the correct passphrase once. Luckily, I was even able to reproduce it after a couple of more retries! However, it took me another five minutes to figure out what was the problem, now that it seemed natural to correctly type my passphrase again. In the end, it turned out my fingers forgot to capitalize a letter.