Unforgiveness is like me drinking posion with the hope that it harms my enemies. When I forgive someone I turn the situation over to powers that are bigger than myself. If someone wrongs me it is the christian thing to forgive them, but that does not mean that I will be inviting myself to have amnesia. That persons actions may have permently altered or destroyed any trust and I may be most comfortable when that person is not near me.
Here is a simple phrase Forgivness is me giving up the desire to want to personally inflict harm on the other person. I am going to say a phrase that it is impossable for a non believer in JESUS CHRIST to understand, but when someone wrongs you, they are forgiven (I turn the matter over for GOD to deal with) and then I need to use dicernment. Believe it or not there are people that think that they can mistreat christians indefinately. Some people say the words "I am sorry" and what they mean is that they are sorry for getting caught. The meaning of true repentence is to not only recoginize the wrong that was done, but to also turn away from the action and not do it again.