SimSpead touched an other aspect of trading, you have to have a close reign on your emotions and feelings. A trader who gets upset because he lost a trade and tries to "get even" is asking for trouble. Also trading when one feels down or any disconfort. I am not here to advertise or advocate, but the best book on the subject is: The Disciplined Trader: Developing Winning Attitudes by Mark Douglas.
I hope it helps guys.
