God advises us to forgive because dwelling on past mistakes is painful and insignificant, and can destroy a special bond. As hard as it can be sometimes, we must forgive and forget just as God does for us. Forgiveness provides a new path way for us to move on and to learn from our mistakes.
(Proverbs 17:9) "Love prospers when a fault is forgiven, but dwelling on it separates even the closest of friends."
(Proverbs 19:11) "The wise know how to hold their tongue; their grandeur is to forgive and forget."