It is not a question of forgetting the past (time is the only solution, which varies in individual case depending upon so many factors); it is about accepting the past. He is not able to forget because he is not able to accept it. I do not think you can go back to original spotless relation; you have to carry on with some tint. I suppose, no male can ever take this in a positive way (that’s how males are!!), I foresee break up here.