The movie 21 has some fantastic lessons for day traders. Although the movie is technically about gambling, its most important lesson is about how to avoid the riskiest parts of gambling and, consequently, how to avoid losing what you risk. Day trading certainly involves risk, but is also most challenging when it takes on the worst aspects of gambling.



The movie was inspired by the true story of MIT students who mastered the art of card counting and who took Vegas casinos for millions in winnings. The main character of this movie, Ben Campbell, needs a way to pay for tuition at Harvard Medical School. His brilliant statistics professor, played by Kevin Spacey, reveals a plot in which he and some of the most gifted MIT students try to bust Las Vegas by counting cards at the blackjack table. After some initial hesitation Ben decides to join the crew.

In a key scene, Mickey, the statistics professor, asks Ben: "Are you in?" Ben answers: "Yes, I am in." Then Mickey looks Ben straight in the eyes and says:

"There's one more thing, Ben, and this is important: We're counting cards; we're not gambling. We're following a specific set of rules and playing a system. I've seen how crazy it can get at these tables, and sometimes, people lose control. They give in to their emotions. You will not! You understand?"

The next day the professor and the students fly to Las Vegas and everything works as planned: they play their system, follow the rules, and win. After returning to Boston, Ben receives his cut: $16,700. He needs $300,000 to pay for his tuition, and so Ben and his friends take 15 more trips to Las Vegas, winning every single time.

After 16 trips Ben has won $315,000, enough to pay for his tuition. But, intoxicated with his success, he gets greedy and will not stop. Finally, one night, he gives into his emotions and loses $200,000 - more than 60% of his account.

While we could say that this is simply a Hollywood story told for pure effect with no connection to the intricacies of successful day trading, we would be wrong. The exact same thing happens to traders every day. At first, they develop a detailed and well-researched system with clearly defined rules, just like the MIT professor had designed. However, one day, especially if their system has been successful, they give in to their emotions and suffer a devastating loss.

The lesson here is about consistency and staying committed to your system, just like Mickey told Ben. You can succeed at day trading when you stop thinking of yourself as gambling and when you realize that you are successful not because of luck but because you have developed a consistent system to gain more than you lose. A gambler takes risks based on emotions, like hunches and greed, and hopes that a few big wins will make him rich quick. A day trader, however, knows that success if defined not by a big win but by a system's consistency over a long period of time. If you want to change how you're trading, change the system based on careful attention to evidence that you've gathered while watching your system work. Never abandon your system because you get greedy.

In other words, the lesson of 21 is, of course, to avoid Ben's fate. Always follow the rules that experience has proven to be successful, and never let your emotions convince you to abandon that system. If you do, you'll quickly learn, just like Ben did, that winning big may take a bit of luck, but losing can be predicted.