It used to take me quite a while (if at all) to forgive people, but I am finding over the past couple of years that I've walked with Jesus and the more I dwell on God's forgiveness shown to me both on the Cross and now in my everyday life, the quicker and easier it is to forgive others regardless of what they do to me. No one will ever sin against us nearly as much as we have sinned against our holy and righteous God, and yet through the Cross He forgives us both completely and instantaneously. That fact alone gives me both the ability and the desire to forgive others completely and almost instantly (I haven't quite perfected the "instantly" part yet, but I am slowly getting there - lol).
It took God many years to get me conformed to this point, but thankfully He did, for forgiveness is something we need to give as much as receive, as Julianna quoted Jesus as saying "If you do not forgive men their sins, your Father will not forgive your sins" - Matthew 6:15.
"We owe so much to a forgiving God, we dare not withhold forgiveness from others."
- Raymond B. Dillard, Faith in the Face of Apostasy, Chapter 7, pg 96
"We need not look up into heaven to see whether our sins are forgiven; let us look into our hearts and see if we can forgive others. If we can, we need not doubt that God has forgiven us."
- Thomas Watson, A Puritan Golden Treasury, pg 111