A very popular saying about forgiveness is that withholding it is like drinking poison and expecting the other person to suffer or die. Of course there’s a lot of easily recognized truth in that statement. The first truth is that the only person being negatively affected by the unforgiveness is the unforgiver. A second truth is that the person withholding the forgiveness is actively trying to harm the person who should be receiving forgiveness. Think about that for second. Withholding forgiveness makes one an avenger, which is something for which God strongly disapproves (Romans 12:19). And if you maintain that position of unforgiveness you are actively opposing God. Further, you are not following the example set by his son (John 3:16).
A very non-Christian thinker recognized some of this truth once when he said that “without forgiveness, life is governed by an endless cycle of resentment and retaliation.” If you haven’t forgiven someone, then you are very likely mired in either resentment, or even hatred of that person, or you are either openly, secretly, or unconsciously scheming to execute retribution, or to exact revenge. And if that is your state of mind, then you are not going to be able to fully love the people around you to whom you are actually committed, and for whom you have nothing to forgive, because a piece of you will always be devoted to harming the person who harmed you. And if that is the case regarding your relationship with the people who you love and can see, what does it do to your ability to fully love God, who you can’t see (Matthew 22:36-39)?
No doubt, forgiveness can be a very difficult task. However, one thing that helps to make it less difficult is to realize that you also are forgiven by God when you ask for it. Each time that we sin against God, we damage the creation that he has made. Sin harms the spirit that he put inside of you. It harms the body in which your spirit is kept. It harms the people around you who he made. It can even harm the very planet on which you walk. And even though all of that is true, God has chosen to forgive you in ways that you cannot fathom (Psalm 103:10-14). He does not deal with us according to our sin.
Unforgiveness is a kind of rivalry, or dissension, or division. As such it is wholly an act of the flesh (Galatians 5:19-21). But forgiveness is an act of the Spirit, and if we live in that Spirit, we will produce different fruit (Galatians 5:22-26). So if you need to forgive someone, if you want to get out of that cycle of resentment and retaliation, and if you want to love your family and God to the fullest, leave your anger at the cross, walk in the spirit of God, and ask him to help you to forgive those who have harmed you.