Agree with Bill and Sandman. You can't forget the person you were in a relationship with. No one ever does. But you can reset your boundaries by stopping contact with him -- no excuses or justifications for it either. The only way to reset is to stop communicating altogether.

The only realistic action you can take, is to stop contacting him, and just resume your life without him and adjust to being single again. Doesn't matter what activities you do, as long as you do them without including him.