Your missing the point dear Sister, but don't feel left out, most miss the point too.
We are currently living in the Kingdom of God and Jesus is King without question. We're not talking about the destination, we are talking about our duty as members of Gods Kingdom, here, now in Gods present Kingdom.
Our Job is to do Gods will, and by doing His will we enter into His Kingdom, here, now. It's not a kingdom of this world where there is worry, hatred, strife, lies, and deceit. It's a Kingdom where peace and harmony reign and we have the choice to live into the Gods Kingdom or live in this world, here, now.
When we hold grudges and fail to forgive, we don't release that person from their sin. Instead, we bind that sin upon them and by doing so, create division where unity should be. There is no harmony, no peace where strife and division dwell so as long as we hold grudges and we don't forgive those who sinned against us, we cannot enter into Gods present kingdom where rest and harmony are found. Yes, I am talking about spiritual and emotional matters because what we do is often based on what we know and these result in what we feel.
If we fail to forgive and we bind those sins upon others, there will be a day of reckoning when we come before the Lord and the matter will be settled by God, and we will be held accountable for our actions. However, if we forgive, then the transgressor will not be held accountable on the day of the Lord because he has been loosened from the offense. This is just a fancy way to say the matter has already been resolved, so it never makes it in front of our judge.