I know what you mean about staying calm. When she started in with her attitude after the game, my first thought was to go off on her and tell her what an a$$ she was being. I was really pissed. But, if I have learned anything, it is that doing that doesn't help me at all. It helps reinforce to her that I am the way I am and it will never be any different. It has a much better effect on both of us to call her out in a calm fashion. It keeps my blood pressure down and by walking away and not letting her berate me or get baited into an argument, I can remain calm and let her stew all she wants.
I'm not excelling, but I am still learning and, I guess, fine tuning things.