Good question!
In my view, forgiveness begins with recognizing that a wrong has been done, a sin committed, a trust breached, and considering the effect that offense has on you. It involves giving over to God all punishment, retribution, vengeance, and "getting even". All that is laid on Christ, Who took the penalty for all sin. Forgiveness is made complete in the heart when one chooses not to rehash the offense but instead repeatedly takes it to the cross. In a nutshell, it is choosing to consider the offense fully "dealt with" in Christ.
Which all sounds very nice until you have to do it.
Forgiveness is not restoration of relationship, it is not choosing to forget the offense ever happened, and it's definitely not putting the issue in storage until you need ammunition against the offender.