Rejection is always hard to deal with. You can't help but asking yourself over and over "WHY???"
Depending on how intense the relationship was....will depend on how long it will take to get over it. I saw a formula about that on the net last year and laughed when it said it would take me a year. I thought SURELY it wouldn't. It did. HAHA!
So, don't beat yourself up over it. Just try to focus on other things....date other guys....and one day all he'll be is a messed up memory!