If you don't have any kids/financial ties/etc. with your ex you could think about going no contact. It has to be for the right reasons though and not for game playing or validation.
Some men are very persistent and it's a bad feeling (prolonged pain) for him to fight to get you back only to do the same things again. So, don't get fooled by his persistence especially if he is unable to clearly identify the problems and outline a plan to work through them.
One more thing - This sounds crazy but if your ex left you or won't speak to you, use it to your advantage. Let pride help you out here. (I know all about this).