obsess

Etymology

From Latin obsessus, perfect passive participle of obsideō (“sit on or in, remain, besiege”), from ob (“before”) + sedeō (“I sit”); see sit, session, etc.; compare assess, possess.

verb

1. (passive, constructed with "with") To be preoccupied with a single topic or emotion.
   Some people are obsessed with sports.
   The [Isaac] Newton that emerges from the [unpublished] manuscripts is far from the popular image of a rational practitioner of cold and pure reason. The architect of modern science was himself not very modern. He was obsessed with alchemy. 2014-06-21, “Magician’s brain”, in The Economist, volume 411, number 8892
   Over the past few months, RAIL has frequently condemned the Department for Transport for its growing contempt for rail customers - by obsessing on cost, caring nothing for service, and not having the slightest interest in growth. August 9 2023, Nigel Harris, “Comment: Disinterested and dishonest”, in RAIL, number 989, page 3
2. (transitive) To dominate the thoughts of someone.
   Thoughts of her obsess my every waking moment.
3. (intransitive, colloquial, construed with over) To think or talk obsessively about.
   Stop obsessing over it, will you!