I would think about it the other way around: What happens if you don't forgive? Is it something you could bear the rest of your life? Would that affect your inner self and perhaps put a shadow on it? What are the practical implications of non-forgiveness, losing a friend, a divorce?
At the end, forgiveness allows us to go on in life. Sometimes, you can go on without having to forgive, but I think it's more often that you get stuck if you insist too much on your feelings and aren't willing to give in.