@mousy,
Mousy - all I can say is WHAT?
Forgiveness is a choice. The choice to turn the other cheek.
You can choose to stop the cycle of negativity.
Forgiveness is the realization that we are all flawed and that we make mistakes.
Remember Jesus saying "Let he who is without sin cast the first stone".
Forgiveness is not possible if you choose to dwell on the negativity and you draw power from it. Choosing not to forgive is a sign of personal weakness.
Choosing not to forgive comes from the power of being a victim.
If we truly forgave one another more often this would be a better world.
When not to forgive? When the other person habitually takes advantage or harms you.
That is blatant abuse and I wonder if that should be forgiven.
... but Jesus would probably say to forgive them
.... it is God's job to banish them to Hell.