How many times must I forgive?

A selection from "When Sinners Say 'I Do' ", by Dave Harvey:

...In the eyes of our compassionate and loving God, sin is sin, guilt is guilt, and all sin is against his limitless holiness...but...God was inconceivably benevolent toward the ungrateful servant (representing us) who by his behavior demonstrated that he had completely missed the significance of what had been done for him. ...As one of the Puritans in the Valley of Vision prayed, "Let me never forget that the heinousness of sin lies not so much in the nature of the sin committed, as in the greatness of the Person sinned against." ...Sin is infinitely wicked because it rejects the one who is infinitely holy and good. The more we recognize the perfection of God's holiness, the more obvious this truth becomes.

How can we not forgive our brothers and sisters, and even our enemies, if God has forgiven us so much? If we do not forgive them, we become like the ungrateful servant, who, after being forgiven our 10,000 talent (think, $1 billion) debt, we go out and find the brother who owes us 10 denari (think, $10). So too, will God call us to account for our actions - "You ungrateful wicked servant! I forgave you all that debt because you pleaded with me. And should you not have had mercy on your fellow servant, as I had mercy on you?" (Matt. 18:33)