The role of a trader can be reduced to two basic tasks:
1) Manage risk
2) Earn a return
First and foremost, a trader must protect precious capital. A trader accomplishes this several ways. First, a trader must know when she or he is "wrong". In other words, prior to entering a trade, one must decide beforehand where to exit the market in the event of adverse price movement. Secondly, a trader must establish a criteria for "slowing down". After a string of losses, no matter how small, one should seriously consider verifying that he or she is trading according to the plan.
It is only after managing risk that a trader is able to focus on earning a return. The allure of the markets is deceptive. Many flock to trading seeking profit, but the vast majority of individuals fail. In my opinion, the primary reason for this failure is a lack of proper risk management and an inability to plan and reassess one's edge.