Why are you so emotional? So the answer must be to think without emotions.
Look at this article again. Read here.
What do you think Bruce Lee was talking about? Is that an emotion?
In almost all things except maybe a very dry technical subject, emotions are invloved. Emotions are involved in all bigger decisions.
Bruce says not anger. But is there an emotion that foisters the fighting spirit that is not anger, hatred? Have you seen an Aikido master fight?
I was once at a seminar where the facilitators (Americans) called up a lady and began insulting her. To me it was insulting. Her failures at a project was broadcast to all without understanding her background. The funny thing was her response. She tried to treat it like a joke. She was so embarrased she didnt know what to do. I thought giving the guy a slap in that circumstance could have been more appropriate.
Actually all our decisions over a chess board/in life is reflected by our emotions at the moment. If we are angry, frightened, indecisive, surprised etc. We need to always see what the appropriate emotion to any given situation should be. If we are insulted, if we are cheated.
Chess is an interesting game is it not? It allows us to examine how our emotions affect our decision making.