You can't let go until you are ready. Sometimes it takes a year. Sometimes, it takes 4 minutes. You can't MAKE yourself let go of the past. It happens over time...and it depends upon how badly you are hurt and what good things happen to you in the next 24 hours, week, month...etc.
Stay busy, even if you are stuck in your room and can't face the world. Play simple computer games like sudoku. play hearts or backgammon online with people from around the world. Don't watch tv...it's a cluster mind-f**k.
actually...I have something for you to try: Read my article and listen to the songs about breaking up...even if that's not your problem. I promise there are no country western songs...well, nothing dumb. REALLY, try my link
These songs will make you feel better, or at least not feel like you are the only one who goes through this s**t. I have a song article for guys but guys will have to look for it on the same site. no link.