I am SO ANGRY that i dated such a twit, how do you deal?

This guy I was dating turned out to be the biggest unfeeling, incapable of empathy, foolish selfish loser. I am in total shock and awe finding out what kind of person he really is - I feel so ANGRY. I can't believe I ever associated myself with someone like him. He's out of my life now but I am so angry and I don't know what to do with all this anger towards him. I really need some good advice on what I can do.