Literally forgetting everything sometimes

Need to be very clear that this is most likely not some kind of anxiety problem.

Every so often I just forget everything. I can study something for months or develop certain habits, and one day it'll just vanish. I'm getting very frustrated trying to draw an extremely simple character because despite the fact that I understood perspective last week, I don't seem to now. I take notes, record timelapses, whatever - doesn't help. It's like I can't develop muscle memory at all. It just happens sometimes and those skills don't always come back; I have to relearn them from scratch, almost. How do I fix it? It's exhausting not remembering how to do something you know you've done before.

I am also not a beginner and "those skills will build over time the more you do them!" isn't helpful. I am also not taking extremely long breaks. Sometimes it happens a day after I have a "good" day.

I know this must be so frustrating and disheartening, and I'm sorry you're going through it.

To a small extent, a little bit of regressing in the learning process is normal. The extent that you seem to be describing sounds pushes into the territory of a disorder or medical issue. I don't know that the general advice this forum can provide will be able to help you in a way you're satisfied with. This may be something that requires medical attention (which I recognize is very hard/lengthy/traumatizing/expensive to access in a lot of places.)

Unfortunately, "those skills will build over time the more you do them!" and "Take notes, record timelapses, etc" are the advice that the art community is largely going to be able to provide you with.

Nono, I appreciate it! I actually am working on that but I can't find a cause so far - I don't think it's going to turn out to be dire based on the tests I've already done, but it's frustrating in my day to day. Posted because I have about 48 hours to finish a piece for an event, have already asked for an extension, and cannot seem to make it work.

For the other advice, yeah, it works for most people! Definitely not disparaging that, more that I already do those things.