I've never been sure what's harder, having a broken heart or fearing you may have caused one.
In either case, first and foremost, you must love yourself. It's what will maintain you and allow you to keep your health and sanity.
Lots of people have mentioned time, and I have to agree with that. I found that my dreams were a good indicator of how much I was getting over him. The scenarios began to change, and slowly I was no longer dreaming of seeing him or being with him. My dreams allowed me to create a different, more livable history to help heal me.
Now, it's been a decade, I no longer dream of him. The heart is no longer broken, but will always bear a small scar.
I love what Rapaire says above...think I'll re-read it!