"Forgiving others really isn't possible unless we are living in light of God's forgiveness ourselves... When we say, "I just can't forgive that person for what he did to me, " we are essentially saying, "that person's sin is greater than mine." Our awareness of our own sin is very small, while our awareness of another's sin is very big. Our underlying feeling is that we deserve to be forgiven but the person who offended us does not. We are living with a small view of God's holiness, a small view of our own sin, and a small view of the cross of Jesus.
But when we embrace a gospel perspective on our own sin, we recognize that the sin debt God has forgiven on our behalf is greater than any sin that has been committed against us. And as we grow in our awareness of God's holiness, we begin to see more clearly the distance between his perfection and our imperfection. As the significance of Jesus' work on the cross grown in our consciousness, our willingness and ability to seek restoration with others will also grown. After all, if God forgave the massive offense of our sin against Him, how could we not forgive the sin of others--which, though it my be severe, pales in comparison with our own guilt before a holy and righteous God?"
The Gospel Centered Life- Bob Thune and Will Walker