I don't know if this is kind of what you call a thought loop, but I go through times, usually triggered like yours, where I just get stuck on a topic and go over and over it for hours trying to resolve the problem. It's usually anger or anxiety that triggers it for me. I'll spend hours going over what they said and what I said and what I should've said and sort of mentally role-playing different scenarios that could've happened. Or I'll spend hours fretting about something that might happen; what they might say, what's the best thing for me to say back, how I should behave etc etc etc.

I don't think I've ever figured out how to stop it though. Usually it happens in bed when I'm trying to go to sleep, and I'll just go on and on and on for hours until I eventually pass out with tiredness. I did this just last night in anticipation for my pdoc appt today! I've actually done this for as long as I can remember.

*Willow*