Duff it can be hard to let go the emotions you invested into the relationship, frustration and anger being high up there. It will take time and distance to be able to mentally shrug a 'whatever, asshat, I know the truth, and somewhere in your tiny self absorbed brain,you do too.'
The happier you become in your separate life, the easier it will become to let go the frustration. I found working out ( don't you run?) got rid of a lot of my anger at mr t mark one!