One of our cats, Mama Cat, so named because she looked to have given birth many times in her homeless life, came to live with us via our backyard. She moved in and insisted on coming into the house and taking over. There were 4 other cats there already. She was built like a tiny bulldog, had the personality of a junkyard dog, and was clearly in control of all the cats in her vicinity. She fought with dogs and cats alike when she was outside. This little all black cat had decided we were to be her new family and so we were.
Now she has been with us for 4 years and she has learned to trust in that time that there will always be food, always be a lap to sit in, always be love and affection given freely. Her personality has changed completely. Now she is affectionate with us and at least tolerates the other cats! She also plays. One thing that hasn't changed is when she runs in the door every time it's opened to let her back in. I think she still doesn't completely trust that she'll be allowed back in. Trust is hard, but she has come a long way. Complete trust, well...every day a bit more :)
Love makes all the difference. It transforms and heals. I have this cat and love design here. I think loving an animal really can heal the world. It can heal an angry cat and that cat can in turn heal us with her love and affection.