I don't know if this is the right place to post this but something very horrible is happening to me. And I wanted to know if anyone can relate to it. It's worth mentioning I'm somewhat advanced in my undergrad as a physics major (3rd semester). The thing is this (although it probably includes more things than the description I'm about to give): All of a sudden, negative numbers make no sense to me. All of a sudden I don't know what acceleration is. I don't know why its a constant here on earth. I dont understand how all forces are reducible to F=ma. I don't understand simple stuff like the distributive property or whatever, and other algebraic steps. I have the feeling I don't understand what addition and substraction is. Although I do understand all this! I love math and love proofs and theorems, so I know why all of those things are valid. For some reason, I have the same feeling you get when you don't comprehend something, even though I do understand all of this. It's incredibly frustrating, I don't know whats up. It's like I have the feeling of not-understanding even though I do and it's bugging me all the time. Has anyone had this experience, and know what to do about it? I've been trying to ignore my thoughts, but it's pretty darn hard. Thanks for listening. Edit: I realise this post might make me sound pretty dumb or whatever, put please consider I am a top student, with excellent grades, who has seen "advanced mathematics". Something is seriously wrong here. Thanks.