Forgive and Forget?

Forgive and forget rolls off the tonngue so easily, but how accurate is it really? Must you forget in order to forgive, and can you forget without forgiving?
I think it's quite possible to forget without forgiving. Years later something could remind you of an incident, and your mind would awaken to find you still hold a grudge. Forgetting is more a slip of the mind than any actaul progress in the emotional department.
I'm sure it's possible to forgive without forgetting but things probably dissapear from memory when there is no longer a reason to remember. I'm not sure I resolved this in my mind by even writing this post.
My conclusion is that you have to forgive to really forget, but might not forget upon forgiving.