Unforgiveness, resentment, harbouring bitterness won't change anything with the situation or with the other person. But it will eat us out. A grudge weighs heavy on us. Satan rides on it and tells us lies, such as, "We have a right to be angry, we are justified – look how they treated us." We need to protect ourselves. Resentment and anger destroys us. Nothing is too deep for God's grace and the Holy Spirit to reach down and remove it. Don't listen to the accuser. Deep-seated anger, pushed down over many years, will manifest itself in other ways, such as depression, hopelessness and despair. There is always a root cause, and this needs dealing with in prayer and wise counsel, or perhaps with a trusted friend.