1. No contact.
2. Reconnect with old friends that you might have lost contact with over the course of the relationship (single friend vs. couple freind BS).
3. Begin talking to other women in order to remind yourself that you are indeed attractive to them.
The third point is the most key, but 1 and 2 really help set it up. It helps to have no thoughts about the bitch (such that you can move on and raise your self-esteem), and meeting women is very difficult IMO without a wingman or a supportive group of friends, especially at first. (partially due to your own insecurities that everybody else shares, and partly due to the concept that women seem to be more comfortable talking to somebody who is with other people). With practice it becomes easier to flirt with women on your own at school, jobs, or waiting in line to get coffee or at the airport, but first and foremost you need a reminder that you are valued by the opposite sex (or, in general terms not directed at the OP, whichever group or demographic you are attracted to).
I just had a great trip out of town and was one cousin's horrendous cockblocking and the fact that I only brought my B-game* away from hooking up with what would have been the most beautiful woman thus far for me (first time really hitting on a girl in 8 years, as opposed to harmless flirting, so not bad), and I later learned that had I found better opportunity I totally would have finished that shit. I will probably regret not cancelling my flight and staying, or not taking advantage of a few more opportunities, or not being more assertive as far as pushing my hopeless ass cousin out of the way (this was the penultimate blow, as he blocked me from my perfectly planned and would be perfectly executed opportunity, girl was married with her drunk husband hanging around so it wasn't like there were many to go for the kill) for the rest of my life, or at least until I get back out there, which I absolutely will do to see my other cousin (the one I really went over to visit, not the cockblocker) and get another opportunity, this time without the environmental complications.
Knowing that this is the best looking woman I have ever had go for me (and there are not many that look better), even if I missed my opportunity (so far, for the next few months to a year anyways), has made my impending breakup with my almost decade long girlfriend a million times easier (she tries to take credit for how much more confident I have become since we began dating, in an attempt to keep me down I believe). The point is, just talking to girls and getting yourself out there boosts self-esteem tremendously. After a rough relationship, a partner will make you feel ugly, when you are not, and sad and lonely, which will project negativity and unavailability (particularly) onto the world making you unapproachable and less appealing and noticeable than other guys (or girls). Get... yourself... out there! By any means necessary. One good conversation with a new girl is all it takes, whether you are looking for a fun bedroom and drinking/clubbing partner, a nice medium term relationship, or the real thing in a girl to marry, you need it to break out of the funk.
*B-Game is defined as game such that you have done most things right, but you did not take advantage of every single opportunity. Additionally, B-game can be interrupted by friends with poor manners or unfortunate dramatic happenings. When you are bringing your B-game, the idea is that you will get there eventually, or would have gotten there if not for unfortunate events. 75% chance of success.
A-game is defined as an unstoppable night where you have the answer to everything. Most people pull this off only a few times in their life, although some people better than me at this are capable of it on a nightly basis. Astounding.
