You will never have to forgive anyone more then you yourself have been forgiven by God. Unforgiveness will leave you miserable. We forgive for our own happiness and benefit. When we do not forgive resentment and bitterness can defile all aspects of one’s life. Forgiving means to give up all resentment and the ability to exact revenge to get even.
As we are called to be more like the Son of God (1 John 2:6) we can know how much we are in his likeness by our love and forgiveness of others. You know the grace of God as much as you are able to show it to others. No one will ever deserve to be forgiven, we must forgive because God forgives us. We judge and condemn others because we have not forgiven them and have not sought to bless them and see them bettered. When we pray the Lord’s Prayer (Matthew 6:9-13) we say to the Lord: “Come, O Lord, and forgive me my sins even as I forgive those who sin against me.”
On speaking of those who would come to partake of communion with unforgiveness, John Chrysostom says, “As it is not to be imagined that the fornicator and the blasphemer can partake of the sacred Table, so it is impossible that he who has an enemy, and bears malice, can enjoy Holy Communion.” Our Lord teaches us to seek forgiveness first before worshipping God, for we ourselves need forgiveness to enter into his holy presence (Matthew 5:24). Of the many sins we can commit unforgiveness is a terrible sin, it is refusing to do what God himself did in offering his Son to forgive our sins. When we harbour unforgiveness we are helping the devil to expand his kingdom as it is a kingdom of accusation, unforgiveness, slander, lies and evil. John of Kronstadt says, “Forgive them that trespass against you with joy, as a good son rejoices when he has a chance of fulfilling the will of his beloved father.”