“Anyone with average intelligence can learn to trade. This is not rocket science. However, it’s much easier to learn what you should do in trading than to do it. Good systems tend to violate normal human tendencies. Of the people who can learn the basics, only a small percentage will be successful traders.
If a betting game among a certain number of participants is played long enough, eventually one player will have all the money. If there is any skill involved, it will accelerate the process of concentrating all the stakes in a few hands. Something like this happens in the market. There is a persistent overall tendency for equity to flow from the many to the few. In the long run, the majority loses. The implication for the trader is that to win you have to act like the minority. If you bring normal human habits and tendencies to trading, you’ll gravitate toward the majority and inevitably lose.
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Decision theorists have performed experiments in which people are given various choices between sure things (amounts of money) and simple lotteries in order to see if the subjects’ preferences are rationally ordered. They find that people will generally choose a sure gain over a lottery with a higher expected gain but that they will shun a sure loss in favor of an even worse lottery (as long as the lottery gives them a chance of coming out ahead). These evidently instinctive human tendencies spell doom for the trader—take your profits, but play with your losses.
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One common adage on this subject that is completely wrongheaded is: You can’t go broke taking profits. That’s precisely how many traders do go broke. While amateurs go broke by taking large losses, professionals go broke by taking small profits. The problem in a nutshell is that human nature does not operate to maximize gain but rather to maximize the chance of a gain. The desire to maximize the number of winning trades (or minimize the number of losing trades) works against the trader. The success rate of trades is the least important performance statistic and may even be inversely related to performance.”
~ William Eckhardt, interviewed by Jack Schwager in The New Market Wizards: Conversations with America’s Top Traders