Everyone wants mercy, but its a lot harder to show it than it is to receive it. In this parable, usually referred to as The Parable of the Unforgiving Servant, Jesus gets to the heart of one of the most impactful realities of the Kingdom, which is the deep and extravagant grace of God.
But the reality of God's mercy makes such an impact on those who receive it that the only proper and right response is to extend mercy to those in need. Jesus' warning here is confronts us all. If you withhold forgiveness from someone, no matter if they have sought forgiveness or apologized, then Jesus claims that this is evidence that we have not experienced the mercy of God. In the life of the kingdom, forgiveness and mercy are free flowing markers among kingdom citizens.
So the question is: Is there anyone from whom you are withholding forgiveness?