I constantly feel guilty because of things that I rationally know are no big deal. It's driving me crazy. I try to ignore the thoughts, but they don't go away unless I "solve" them, i.e. I manage to convince myself that the feelings are indeed not justified.

Example: I took a test in school recently where I had to compare a story to a text we'd read in class. I couldn't remember what was said in the text, so I just took a stab in the dark and wrote whatever I thought most realistic to have been in it. I got an A, so I must've gotten the content of the text right, but now I keep thinking "I don't deserve the grade because I didn't remember the text. I wasn't sure, I just guessed. I just got lucky. I'm a fraud."

I know this makes no sense, I know I didn't cheat and what I wrote in the summary is my own work, no matter how unsure of it I was. But I just can't convince myself, I can't believe in it. The feeling of guilt, of being an undeserving fraud, is dragging me down.

I constantly have thoughts like this. I wish so badly that I could just ignore them, not dwell on them, just tell myself in advance "it's illogical" and just let it go. But I can't. They ruin my entire day until I've come to a positive conclusion, which can take a long time.

How can I fight these recurring feelings?