" anger has a bad reputation. It’s a negotiation device that helps us stand up for ourselves, to say, in effect, “Get off my turf; you’re stomping on my sense of self. Stop crossing into my backyard.” Then it’s up to the other person to deal with your anger—to decide whether it’s a legitimate problem that requires a change in his or her behaviour. “Your mother was hurt, and then she considered it, and she hasn’t mentioned her ‘mother fantasy’ since,” I said. I emphasized that anger is a signal that someone wants to be treated differently, which is healthy; cruelty is when someone deliberately wants to hurt someone else. "

― Catherine Gildiner , Good Morning, Monster: A Therapist Shares Five Heroic Stories of Emotional Recovery