I can probably think of a dozen reasons why not to forgive someone or something that’s negatively affected me. Come to think of it, there’ve been a few someone’s and something’s!
On the other hand, there’s only one reason to go through the forgiveness process, and it’s not because of ethics or a spiritual preference or because I want to be morally pure, (although that would be nice).
It’s because the physics of forgiveness releases me into higher dimensions beyond the duality we’ve been born into.
A door of potential, learning and growth opens for me, as I access other, happier ways of feeling and being.

Just about every spiritual practice seeks to overcome the entanglement of opposites that ‘concretely’ define our material world and who we believe we are. Without exception we identify something relative to something else.
However, in a single act of grace – (which just means the ability to show acceptance and mercy to ourselves and others), we can step out of our struggle with attractions and aversions through forgiveness.
By freeing myself from being focused or entangled (read trapped) within the 3rd dimension where duality reigns, I can freely hook up with ideas and inspiration from higher dimensions.  I am freed from the push and pull struggle of entanglement, to be inspired and grow and choose the direction of my evolution. So can you, because that’s physics!