For me, it's messing up/ doing something socially unacceptable or hurting someones feelings without noticing. In my life I've done this many times, and the times it happened the worst were when I was having a lot of fun, and had no idea I was doing something wrong. I'm the king of miscommunication.

I had a long history of this, especially as a kid, and because of it for a long time whenever I was having a lot of fun in a social situation I'd suddenly remember past times when I messed up, and then I'd go down in a self-doubt spiral and it'd kill my fun and start acting weird.