Usually I am preparing myself to the process of trading, I listen to the calm and positive music, usually I am drinking green tea with mint. You can think that I am kidding but this is real, I'm trying to be as calm as it is possible.
Its look like easy to control our emotion but not so easy. I think it need a good experience in trading which can make you able to control yourself and take a right decision in a right time. So having good experience in trading can enable you to take a correct decision on time.