Those who have had a relationship break up after 5+ years, why? Why did it work for so long and then suddenly just...not?

 I was with my ex for 6 years. We dated from when I was 19-25. He broke up with me in May of this year and it was really difficult for me. I felt everything between us was fine and then, all of the sudden, it wasn't. I realize now that we were never really meant to be. I love him as a friend, but we are two different people. I will always have love for him, but I think a lot of our relationship was lust and that disappeared after the first 3 years. He would get angry with me when I tried to initiate sex and then when I stopped initiating, he would be upset saying I wasn't sexual aggressive enough. It was hard for me (ha). 
The week prior to our breakup, I was out of state for 10 days. Throughout our relationship, he never had his our car. I tend to be an enabler and instead of letting him fend for himself, I let him borrow my car while I was gone. When I came back, all of my "girly" items had been removed from the interior of my car and shoved in the trunk. This bugged me severely. He said it was because he wanted to "change my air freshener", but I am not sure if that is entirely true.
During our 6 years together, there was a lot of turmoil in our relationship. The first 2 years were the worst. He was physically violent and was very aggressive with me. I just figured it was us acclimating to living together and that, with time, it would be ok. He was 30 years old and was ok with working at McDonalds the rest of his life. I am by no means saying there is anything wrong with that, but he couldn't support himself let alone a family. I view myself as very ambitious, and sadly, he was not. It was clear that we wanted different things in life. 
 We had begun discussing buying a home together and he seemed excited at first, but quickly got cold feet. I was fine with it because we were comfortable where we were. I feel like the break up was a long time coming. I don't feel like I would have ever made that step to end it. I am honestly happy that it is over. He was going nowhere in life (as much as I hate to say that). He was very immature and it was exhausting. We could never just talk about problems in our relationship. It always had to be a huge blow out argument that ended in him punching himself in the face or breaking a fucking lamp. I tend to be a passive girl and when he would start yelling, usually I would shut down emotionally. Our fights were always just long continuations of each other. Nothing was ever resolved. I felt he never listened to me and if he ever did listen to me, it was just long enough to tell me how invalid my thoughts and feelings were. I am not saying I was the perfect girlfriend, but I gave a conscious effort.
I don't want to act as if our entire relationship was terrible. It wasn't. We were seriously best friends, who happened to sleep together. We loved the same things. We gamed together constantly and were usually pretty happy. I do not regret the time I spent with him as it made me into the person I am now. Since our breakup, I have "grown up" exponentially. I know this has been long-winded, but sometimes it is better to grow apart and separate then to not be truly happy. 
 Sorry for the wall of text, but it actually felt nice (and slightly therapeutic) writing it out. There are still times where I miss him (had a dream about him last night), but I think I miss his friendship more than anything. Like I said, we constantly played games together, went to the movies, and just joked around. During our relationship, I neglected all of my friends and now they are gone. I need to work on building new friendships, but that will happen when I am ready. I am happy with being alone right now. My ex and I had similar humor and I felt like I could be my nerdy self without judgment. I have decided to take a break from dating until I can truly invest myself in a new relationship.
/r/AskReddit Thread