I do this too and I think, for me, it’s two parts.

1. Neurotic self analysis / self evaluation coupled with
2. An actual interaction where I chose poorly that day.

I over evaluate myself generally, so when I do make any mistake socially, my mind will find out on later self analysis and bug me about it.

I find it annoying now and try to dismiss it and go back to sleep. Half the time the thing my mind is fixated on is baseless anyway.