A head injury affects your mental health, physiological and psychological health are connected in many ways for most health issues but in a head injury they are pretty indistinguishable - is really is all in the head. I've avoided pretty well all of that which I'm really pleased about but I'm mindful to avoid some situations that I could imagine causing issues - worried about not getting a girlfriend again? best avoid the man your last date dumped you for etc.
But one issue I did have last year was ruminations. My mind would latch onto a particular argument I had and replay it over and over. Whenever I was a bit stressed or grumpy about anything I'd find my mind latching onto this issue again and again replaying it in ways and trying to find different reactions I should have had in order to get a better outcome. As I had new arguments on the same topic over the course of the year my ruminations would change to the latest confrontation getting stronger or weaker depending on how well I felt I'd handled it.
The main coping strategy for this would be to close my eyes and say "No" loudly three times out loud (or if it happened when I was dozing and had eyes closed then open them). This would fairly reliably make it go away.
Ultimately it needed diagnosing that it was caused by my inability to do personal confrontation and then working out how to change that and make myself satisfied with what I could do. Then the issue was resolved in my favour and the ruminations went away. Which I'm very pleased about.