dwell on
phrasal verb.to spend a lot of time thinking or talking about something, especially something bad or unpleasant.
phrasal verb.to linger over or obsessively focus on a specific subject, typically a past mistake or a negative event.
“Don't dwell on your mistakes; just learn from them.”
“She tended to dwell on the argument for days, replayng every word in her head.”
“While it is necessary to acknowledge historical failures, we must not dwell on them to the point of paralysis.”
usually followed by a noun phrase representing a negative past event or a worry.
contrast with 'think about' (neutral) and 'brood over' (more emotional/moody); 'dwell on' implies a repetitive, unproductive mental loop.
use 'dwell on' for thoughts; 'dwell in' is a literal, archaic term for living in a physical place.