We were fighting every minute of every day. Over really ridiculous things. There was no respect left in the relationship, it became one of constant criticism and belittling and I had become a husk of my former self. (It's been over 17 years and I'm still not the person I was, I don't think I will ever be.) I finally turned to him and said “It's not supposed to be This hard. I love you but I'm done.” He never would've had the courage to end it. Sometimes I miss him as we had so much in common, but we mixed like oil and water. It was and still is for the best.
It’s funny because when you are younger, everything you read or see, lead you to believe that relationships end for very simple, cut and dry reasons. One cheats on the other or one person moves away. (As an army brat, that was a Big factor.) You believe, when you get older, it will be so easy to solve or avoid these things.
Then you get older and relationships end for reasons you never anticipated. One person wants an open relationship or the other person doesn't see you as “the one” they want to commit to forever. In the relationship mentioned at the begining of this answer, we loved each other but brought out the worst in each other. My 16 year old self, brainwashed by Archies would've never realized that ending in a million years.