"Be kind to one another, tenderhearted, forgiving one another, as God in Christ forgave you." (Ephesians 4:32)
Sometimes it is very hard to forgive someone who has wronged us. Sometimes we don't want to forgive. We want to hang onto the anger because it feels like a way to punish the wrongdoer. But in reality, we become the wrongdoer too when we refuse to forgive.
God forgives us for all of our sins because of the sacrifice Jesus made on the cross to receive the punishment we deserve. Why be a punisher when we can be a forgiver? The truth of the matter is that the one we are really punishing is ourself. When we refuse to forgive, we are allowing resentment and bitterness take up residence in our heart.
God forgives us, not because we are forgivable, but because He is forgiving. God loves us, not because we are lovable, but because He is loving. We need to become like Him. We need to be loving and forgiving, not because others deserve it, but because Christ's love flows through us into the lives of others. When Christ resides in our heart, there is no room for a bad tenant like unforgiveness.