Matthew 18:21-35; Luke 7:36-50
The greater the debts the greater should our appreciation of God be. The forgiveness of our own debts should move us to be humble and forgiving towards others, especially if their debts to us are far less than the debts we owed God which He, in His mercy, cancelled.
The difference between the servant and the prostitute is that her focus was on the Master (Jesus) rather than on the debt.
Forgiving others is not always easy but in order to receive it we must learn how to give it.