Sorry, can't happen [set in time and memory, can't go back, only forward] you could [and should] try coping with what has happened, accept it and move on. It might hurt now, but there was good times, and one day you'll look back and laugh. If you choose to shut yourself away you could do some emotional damage to yourself you'll have to deal with eventually and it will keep getting worse until it's dealt with.
If you need help healing, ask your friends/family to not mention your ex for a while. If possible, avoid him [not forever but limit contact until you feel better] if you have gifts or photos, you don't have to throw them out, but you should pack them away so you can decide what to do when your more emotionally centered and not being ruled by them. Journaling and meditation can help you come to terms with everything.