Break ups hurt-especially if you really loved the person. However, they happen for good reasons-most of the time.
Time is the best healer. Just keep yourself busy-slowly the wound will scab over and not hurt as much. Hang out with good friends, cry, rent stupid movies-just do anything to keep your mind off the hurt.
I know it might seem ridiculous, but in time, the hurt goes away-at least that's been my experience.
It seems like the grieving will never end, but one day you'll wake up and not feel so badly-and each day will be a bit better. You'll have set backs, but over all, you will get through it.
Best wishes.