Perseveration is the act of thinking about one topic for an extended period at the exclusion of other topics. This is different from concentration or being focused. It can go on for hours or, even, days. It's part of a collection of symptoms I have from my mental illnesses. I pretty much hate it because I perseverate on horrible things from the past that I don't have 'resolved'. Honestly, I don't think you can resolve the breech of trust that comes from when your parents throw you out of the house when you're extremely ill in the middle of winter. I had pennies to my name and they were going to leave me with just the clothes on my back out in the street. My Grandparents intervened and that's how I wound up living in east Jesus for a year before I got married.
I grew up on a farm about 5 miles from civilization in any direction. There was literally nowhere for me to go. I've been thinking about this for weeks. I had to deal with threats of being thrown out from the age of 12 through my early 20s. When they did it, they claimed it was because I wasn't pulling my weight as a member of the household. Meanwhile, one brother chain smoked, played video games, and was unemployed for years by that point, with a child. The other brother was in the military but wasted his money on alcohol instead of supporting his wife and children, leaving the rest of the family to do that. And when he was on leave, he would play video games and fuck off to bars in the area to get his drink on instead of going to be with his family. Neither brother cleaned anything, they wouldn't cook, or do their own laundry.
It was my childhood all over again during the time from graduation from college to when they threw me out. I was basically the household serf who had to perform perfectly and be silent. There is a lot of unresolved trauma around all of that. I think that's why I can't get it out of my head. It's part of a long list of things that I am certain I can never 'resolve' only learn to live with.