Forgive but not forget?

Today in Sunday school we discussed Mark 2:1-12 -- a passage where Jesus healed a paralytic man. In verse 5, Jesus said "Son, your sins are forgiven." Isaiah 43:18 "Forget the former things; do not dwell on the past."

Our conversations turned to this conclusion: To forgive is to forget.

In some sense, I agree. People who have short-termed memory tend to forgive others more easily or more often than others... partly because they don't remember or don't choose to remember things for long. I would say that I have short-termed memory most of the time and I forgive others readily. But I do remember things that happened a long long time ago. I don't necessarily hold grudges against those who had crossed me in the past, or do I? But I certainly remember -- most of the time -- who, where and when.

To completely forgive others, do we have to completely forget? Is forgetting a prerequisite to full forgiveness?

To a certain extent, the answer is yes. If we still remember the pain vividly, we still have not forgiven the person who inflicted us the pain. But the problem is, once we forget, how do we learn from the past experience? We always say "learn from history or from the past." We hold this almost as a universal truth. But if we forget the former things, from where do we learn our lessons?

A girl whom I used to date told me at the end of our relationship, "forgive but not forget." To this day, that phrase still rings loud and clear in my head. I still feel the guilt and the shame for what I had done. If she has never forgotten, how can I forgive myself?