I was with/dating a girl a while back, and we seriously thought we were each others' soul mates. So many things in common, talked on a level of intimacy and honesty that took us both by surprise, had a couple sessions online when we'd just chat for 6-7 hours on end. Even silly stuff like having identical "relationship" lines on our palms, and me waking up for no reason at night, and finding out later it was the exact minute she set her alarm to.
I cared about her, deeply. She told me that no matter how much she'd try to pull back, or to push me away, that I should never let her go because she wanted me to be a part of her life for a long time.
...but it didn't work. It just didn't. We'd get into these insane arguments about nothing in particular, and one of us would almost always find some way of hurting the other at one point or another.
We were both rather blind, for a rather long time. Only now, several months after the fact, have I finally realized how it just never could have worked out. It's not that our personalities were completely at odds (I've had that kind of relationship too, we were pretty serious for a few months before it all came crashing down), they weren't. When we got along, we did so amazingly well. But the rough spots just weren't going to go away, no matter how much either of us might have wanted them to.
I wound up missing out on, and eventually completely ruining my chances with someone who really could have been a good person for me, because I was still clinging to the idea of a relationship with this girl.
Things obviously aren't working if you're fighting so often... I know it feels bad to make someone else hurt, it's horrible. It's a poison dagger in the heart. But there are times when you really just can't avoid that, and trying to pretend that you can avoid it is just going to wind up digging it in deeper.
I still care about that girl, to some extent, and I hope she finds what she needs out of this life. That's just the kind of person I am. But I do not regret breaking it off, and I know things would have been so much worse if either of us had tried to drag it out any longer. Only thing I regret is that I didn't do it sooner.
The pain will pass. It'll take time, a lot of time. Months, easily. But it will pass, and it had to be there. I'm going to give you some silly advice that I was given, and that I very rarely followed, but that did help when I let it.
Get out, a lot. Go for walks, runs, whatever. Spend as much time around your friends as possible, you really don't want to be by yourself. It may feel good, but you wind up doing stupid things and thinking stupid thoughts.
Be sound, man. We all have to deal with this at some point. Hope you do a better job than I did.