Contempt is the only asymmetrical expression in the muscular facial system: Disgust, fear, happiness, surprise and anger typically express themselves symmetrically. Contempt is marked by one lip corner pulled up and in a dismissive sneer.

I guess I probably make violent films partly because I can't express my anger in my real life very well.

Genuine expressions of emotion rarely persist longer than five seconds and almost never longer than 10. A fixed smile is likely to conceal anger, anxiety, or some other negative emotion.

Anger Quotes