anxiety troll
The part of your brain that likes to remind you of all the bad/embarrassing things you've ever done to ruin your, otherwise pleasant, day. He's the little asshole that you try and keep locked in a cave, but jumps out when you're not paying attention and tortures you with your own stupid memories...like an asshole. Asshole!
I was trying to go to sleep, but my anxiety troll got out of his cave and I was up all night thinking about that time I made my mom cry when I was ten.