You can't force forgiveness, if it comes, it comes when it comes. Simple as that.

Also, forgive and forget is a really stupid sentiment. I'm a very forgiving person, but I have a stellar memory, and if I forget then how do I remember to keep certain people at arms length?

I think what it tries to convey is, forgive and move forward. That makes much more sense than forgetting altogether.

Anyway, like I said, you can't force forgiveness, you're obviously not ready for that step, so stop beating yourself up.