Don’t try to let go of the grievance. Trying to let go, to forgive, does not work. Forgiveness happens naturally when you see that it has no purpose other than to strengthen a false sense of self, to keep the ego in place. The seeing is freeing. Jesus’ teaching to “Forgive your enemies” is essentially about the undoing of one of the main egoic structures in the human mind. The past has no power to stop you from being present now. Only your grievance about the past can do that. And what is a grievance? The baggage of old thought and emotion.