its all in the mind actually. once you weigh out the pro and cons of the relationship and seriously ask yourself deep down inside your heart, also at the same time believing that things happen for a reason, you will eventually come to a state of acceptance and no more denial- and eventually you will be able to accept the fact that this kind of things do happen. do not let your heart overpower your brain.
I just broke up, and my current wallpaper of my hp has a picture of a brain and it says "use it" ..kinda helps me alot.

maybe