I ripped up cards from my partners ex.

I think you have to to wn up to it and fess up to it, and do what you said: beg. Beg for his forgiveness. But you have to realize that forgiveness in this instance is very much a two-way street and that attaining forgiveness will also very much be a two-way street. While he's forgiving you for prying into and discarding, personal items, you will have to forgive him for having a part of his memory and heart that doesn't belong to you. If you think of your connection to her as a competition, you'll have lost before you've begun. You won't be able to say you're forgiving him for thinking about her, but you're going to have to do that. You're going to let ALL that go, and be satisfied with being with him in the present. That'll be hard under any circumstances, but harder if they have children together. You will have to be incredibly patient, and be silently grateful for his unspoken forgiveness. You can never mention her or express a critical view of her, nor mention your intrusion or destruction. If having him is enough for you, then let it be so, and act like his presence in your life is enough and forget about his keepsakes. If you must think of it in terms of a competition, then recognize that you won it: he is with you. That may have to be enough, and it will be, if you let it. But if you want him to forgive you so you can freely remind him of the keepsakes and crudely rub salt in the wound, you don't deserve forgiveness; you deserve divorce.