Matthew 6:14-15
If you forgive those who sin against you, your heavenly Father will forgive you. But if you refuse to forgive others, you Father will not forgive your sins.
Jesus makes it clear that forgiveness is essential to being a good Christian. Most people want to be forgiven but are slow to forgive. When we hold grudges and let anger seeth, we are spiritually sick. Anger causes stress and stress is the main cause of illness. If unforgiving anger can cause physical damage, imagine what it does to our spiritual beings.
Forgiveness is not the act of saying to someone who has wronged you, "it's okay." We have to realize that its not our place to pardon a sin. Our forgiveness is letting go of any anger that we may harbor and transferring the wages of that sin to GOD who has the authority to deal with it. We canb forgive wrong-doings but we cannot pardon the sin.
Forgiveness cannot be given unless we acknowledge our own weaknesses. We cannot receive forgiveness without realizing our need for it and we cannot give forgiveness without admitting to ourselves that due to our own imperfection, we have no right to withhold forgiveness from others.
Peter came to him and asked, "Lord, how often should I forgive someone who sins against me? Seven times?" "No!" Jesus replied, "seventy times seven!" (Matthew 18:21-22)
It's not easy feat to forgive someone of the same offence 490 times as Jesus told Peter but we must for when we harbor unforgiving anger, we hurt oursleves physically and even worse, we alienate ourselves from GOD who is forgiving by nature.