Many of us find it nearly impossible to completely forgive someone who has wronged us. It eats at us and tears into our soul, but we still hang on and harbor that same spirit of unforgiving.
Perhaps the best response to teh question, "how could I forgive someone who has wronged me?" comes from a Q & A session with pastor/teacher John MacArthur:
...who am I not to forgive someone else, who myself, though not committing perhaps the same sin, am so in need of forgiveness.
Let me give you an illustration, Matthew 18, there was a king and this king had a large territory, and he had apparently some providences and some provincial governors. It was time for him to collect from them the money they had collected in their own providences for taxes. So all these governors came in and it was a time for them to account for what they had done with their responsibility. One of those men came before the king and it says that he owed the king an unpayable debt. He owed him. . . .it uses "murion" which is the highest Greek term for a number, so it is an unnumbered amount, and unpayable amount. Even if it translates 10,000 talents, it's astronomical, because the whole national debt of Galilee for one year was 600 talents. So he owed 10,000 talents or he owed an unpayable sum.
So he falls on his knees before the king, and he says, "Have patience with me and I will pay everything back," and he means well. The king looks at him and says, "I forgive you." Now that king is God, and that man is any sinner, and any one of us who come to the Lord and fall on our knees before Him and recognize that we have defrauded God, and we have sinned against Him, and we can never pay for our own sin, and God then forgives us--we are in the same situation.
Then that man who had been forgiven an unpayable debt who deserved hell, in fact, the king said, "I am going to sell him and his whole family and get all I can get out of them," which is what hell is: not getting what God deserves, but getting all He can get. The guy who was forgiven then went out, found a guy who owed him 300 denari (a few hundred dollars), grabbed him by the neck, strangled him, and the guy said, "Be patient and I will pay, I will pay!" Instead of forgiving him, he threw him in prison.
So here's a guy who has been forgiven an unpayable debt by God; he goes out and he won't forgive some guy that owes him a few bucks, and he throws him in jail, and then the parable says, "That some others who knew about it (other servants) went and told the king what he did, and he went back and punished that guy," and the whole point of the parable is this (and that's just it in a nutshell), the whole point of the parable is this: who do you think you are not to forgive someone who has offended you, when you have so offended a Holy God, as to be in debt to Him to a level that you could never ever pay?
So on the basis of God's free and comprehensive forgiveness of you, you ought to be able to forgive another brother who is a sinner like you.