These things happen in life. Just take care of yourself as you grieve. It is exhausting! My break ups left me wrung out and sobbing like crazy -- and I was the breaker upper! Dealing with a loss is a big thing.
But then get back on the saddle once the initial shock of the break up passes. Just don't put it off for ever. You can still feel sad, but getting back to your normal routine really does help get back to healing.
In time you will be able to notice that something new has begun (a whole new life for you!) and not just the thing that ended. (old relationship). You will feel better, I promise.
A.