'Forgiveness cost God His Son on the cross, but what does it cost us to forgive one another? Forgiving costs us our sense of justice.
We all have this innate sense deep within our souls, but it has been perverted by our selfish sinful natures. We want to see "justice" done, but the justice we envision satisfies our own interests.
We must realise that justice has been done. God is the only rightful administrator of justice in all of creation, and His justice has been satisfied. In order to forgive our brother, we must be satisfied with God's justice and forego the satisfaction of our own.'
-Jerry Bridges, 'The Practice of Godliness'