Rumination
Going over the same thing again and again without getting anywhere. Feels like thinking. Isn't.
Rumination is the loop: the argument replayed, the mistake reviewed, the worry rehearsed, with no new information and no decision at the end. Evidence: solid It feels like working on the problem. It's the mental version of pacing. Evidence: decent
It keeps the stress system switched on, it's often worst at night, and it's a reliable predictor of low mood sticking around. Evidence: decent
Why it matters
The way out isn't to think it through better. It's to break the loop with something physical, write the three lines and the next step, or say it once to one person. Evidence: decent Then the brain is allowed to put it down.
If the loop has run most days for a few weeks and your mood has gone with it, that is a doctor conversation, and a normal one.