It often seems to me the hardest thing to do is forgive. Generally as humans, we don't want to forgive those who have wronged us, even for the most minor of offenses.
Something that you've probably heard from me before, forgiveness is a grace. It's not something that is natural to the vast majority of our beings.
It's a lot easier to hold grudges against people than it is to forgive them. Yes, we pray during the Liturgy, forgive us our trespasses as we forgive those who trespass against us. (from the Our Father) and we do know Our Lord's words of drop anything against one's brother before coming to the altar.
Let us extend the mercy that God shows to us, unto others...so that we might set aside all earthly cares.