i also used to break up (or make the breakups start) right around the time that I started to fall for the person. I think that's attributed to the underlying guilt I still have from 5 years ago:
I can't move on & be happy until he's moved on & is happy.
Breaking the cycle is hard. I've found a guy, I am happy/could be happy with him, and yet... There's this age-old tug to cut & run... to stay friends because I might screw this up again...
I have to constantly check myself. Not constantly, but I'm recognizing that I have an issue and I'm checking it when it flais up, which is different than before. Before I used to give into it & get all hysterical.
Now I'm like, look. This is a good thing. Go with it. He's never coming back, and you're wasting time waiting for him. Look at what's in front of you. Love and let yourself be loved. It might turn out even better than before.
Besides. it wasn't real before anyway.
But it was still the best time of my life.