"For if you forgive men when they sin against you, your heavenly Father will also forgive you. But if you do not forgive men their sins, your Father will not forgive your sins." Matthew 6:14-15
Basically, this is a reiteration of what Jesus was saying in verse 12: "Forgive us our debts, as we also have forgiven our debtors." The community of Christ-followers should always be forgiving, because our God and Father is always forgiving. Some of us haven't realized that we really aren't perfect, and that others aren't either. So why do we continue to hold back forgiveness? I think it may be some part of the old man rising again in us. I don't know for sure, though. All I know is, I should be MUCH more forgiving than I am, and I'm pretty sure each of you should be also.
May you forgive today, regardless of the harm that has been done to you. In doing so, you shall put a smile on the face of the Almighty.