Forgiveness is a process, not an event of a moment. One needs to be prepared to let go of the feelings of hurt. That is not automatic, and struggling with this is not abnormal. Some experiences of pain, abuse, or offense canbe longlasting. It requires much work to overcome that. Just expressing that one is mochel does not mean that true forgiveness has been achieved. The typical ritual of erev Yom Kippur, of, “Are you mochel me?” followed by, “Yes, I’m mochel you. Are you mochel me?” – is basically that which could be accomplished by a verbal monkey or a talking bird. There is nothing but the acting out of a simple script, without the required emotional involvement. The one asking for mechila has as much work to do to be prepared to do so with sincerity and the one granting this mechila.
There is a recent book by Rabbi Dr. A.J. Twerski on Forgiveness (published by ArtScroll). Check it out.