Forgiveness is the flip side of freedom.
When you don’t forgive, you are giving away part of your control to an outside entity. This results in you having less control which also means you have less freedom.
More constraints result in less freedom.
This is why forgiveness is about you. Forgiving is the process of removing the constraints on your freedom.
This is also why forgiveness is so hard. It took time and energy for the constraints to be created and will therefore take time and energy for them to be removed.