1) Find peace - there's nothing as frustrating as mourning over a relationship that wasn't meant to be. Yes! If it was, you'd be together now. No man walks away from a lady he truly wants to be with. Even in the most difficult circumstances, he'll be man enough to work things through with you.
2) Give another man room - clear up his room in your heart, no matter how beautifully furnished it once was, for someone else to come in and occupy. I know even after the clean up, there might be some bits and pieces littering around. That I believe you can handle. And until you give the room out, you won't know how beautiful it still can be.
3) Get over your regrets - it doesn't matter what you did right or wrong, he's gone and the longer you keep regretting, the longer your pain will linger. Such wouldn't be healthy for any relationship you get into. Even with family. Don't go biting everyone's head off. Because you'll always be conscious of what you're doing. Of course, you'll end up loosing a grip of yourself.
4) Be the biggest winner: he left you, its his loss not yours. And the time you're spending crying over him should be invested in improving yourself. He may or may not return but be the best you can be without him. I could imagine there were some things you couldn't do while you were with him. Go on, try them out. Kate Middleton did and had a positive outcome. You could too.
5) Let others learn from your mistakes or boldness: yes! Some other lady may get to learn from your mistakes in losing your man and your boldness in getting your life back together. Your life, no matter how terrible it may be sometimes should impact someone else's positively. The reason your previous relationship failed just may be the reason why your new one may work, different strokes for different folks. Always be real to you. You owe yourself that. Cheers!