I'm curious about why others ended long term relationships (not married or with children). I was with my ex for years, and it ended because I stopped feeling like I wanted to have sex with him, and he was constantly pestering. It had to happen at night and again the next morning, which was too much, and then even after the morning event he would be up for it again. It drove me insane.
Also he used to go away about once a year with his mates on a fishing jaunt. I know there were no other women or anything involved at all, I am absolutely sure. He also would make birthday arrangements for himself without involving me, and then presenting it to me as a done deal - ie spending birthday with mates. Then when I did the same sort of thing and he was miffed. and I said I didn't see an issue as he did this too, I got "don't be like THAT". Like what? I was only living my life.
Also when I challenged him on things, I was told I was vitriolic when I was far from it. Once this was in a restaurant when I disagreed with something or challenged. It was really innocuous, I can't remember what it was, but I would not have been aggressive or vitriolic when out in public. I told him to look vitrolic up in the dictionary.
He had a lot of good qualities, but these became dealbreakers for me and I couldn't be in a committed relationship with him because these things drove me nuts.
We do see each other now as friends, but that's it.