That’s the word for what I do, apparently.
Ruminating is going over and over the same situation(s) trying to find an answer or an explanation or a solution where there is none.
Once I found out it had a name, I googled, hoping to find the answer. No such luck. Google “how to stop ruminating” and you find a selection of articles that all offer trite suggestions (play with your dog! Go for a walk in the woods! Do yoga!) which all basically add up to ….”um, good luck with that.”