Love is the only answer to any question. It is very hard to forget the past and so asking someone to forget the past is almost impossible. What the main issue should be, is to Forgive the past. Look to the future and believe in the person you are with. If by actions and words they are trying to recreate a new beginning, one must take the first step to trust that what they are trying to do is honest.
People are only human and by being so, they make mistakes.
Some of them are so hurtful that the memory of it cuts like a knife. When the memory of the event or events come into ones mind, the person that is trying to forgive has the choice to run with it, or stop it where it is and choose to change the way they think about it. This takes time and committment to wanting a better outcome and future. It is a gift you give yourself. I am committed to making things better each day for us.