It is an act that frees you from the burden you carry by holding onto what someone else has done. You liberate the weight, the energy, the negativity, the blame, everything. When you don't forgive because you think the other person doesn't deserve it, it ultimately becomes something that you have to endure and experience within yourself.
Forgiveness is an act of empowerment, where you empower yourself to be free of the very thing you need to forgive in the first place.
Image "Holy Spirit and Worship"