I didn’t exactly end my relationship, either, but it ended because of me. I’m mentally processing it. In my mind, I focus on all the reasons it didn’t work until my mind comes to terms with it being for the best.
It also helps to get involved in some new hobby, service/volunteer experience, or creative effort.
I used to think human behavior was complex, too, but it’s really not. Definitely not in the sense of small claims court.