For me, the key to successful investing is to approach it like you would a game—a deadly serious game, but still a game. In order to win, you have to:

1. Think in terms of probabilities, not in terms of gut instincts. Every choice you make should maximize the probability of an excellent outcome.
2. Keep in reserve what you need to get you through your month-to-month expenses and treat your funds for investing as “play money.” If you think of it as real money, you may be unable to justify putting a large percentage of your savings into a single security.
3. View setbacks and temporary defeats as part of the game, not part of your real life. This is tough for investors. This year I lost about 30% of my yearly salary in one day; a few months later I gained the same amount in one day. Expect long periods of underperformance and occasional major losses, and don’t panic.
4. Keep a poker face and don’t tell others why you’re doing what you’re doing or how you’re getting the results you’re getting. (This is a rule I break all the time. I should know better.) And when you win, don’t brag about it. (This is a rule I break all the time too. I should know better.)
5. Make big bets confidently. I often put more than ten percent of my portfolio in a single stock. Don’t let diversification become di-worse-ification.
6. Nobody has ever won a game by employing three different strategies at once. Figure out your best strategy and stick with it.
7. Never switch strategies, especially not in the middle of a game. Tweak your strategy instead, improving it constantly.
8. Constantly question what you’re doing and why you’re doing it, but don’t take action on the answers you come up with until you’re absolutely sure. And even then, sleep on it first.
9. Research, research, research. Constantly investigate securities, accounting rules, exceptions to your beliefs, process, and all sorts of stuff you’ve never thought of.
10. Play other, related games. For example, design a strategy for a group of securities you’ll never invest in. Enter stock-picking contests. Make small side bets. You’ll learn a lot from these challenges.
11. Enjoy every moment. If it’s no longer fun, just buy an index fund.
12. Be determined to win, but be even more determined to play, in every sense of that word.
13. And remember, money can’t buy you happiness or love or friendship or family. Those things come first.

Now if your aim isn’t to win but simply to do reasonably well while minimizing your risk, don’t follow these rules—I’m sure you can come up with ones that better apply to your situation. But if your aim is to win—whether that means consistently beating the market, wowing your friends, or gaining a seat in the pantheon of great investors—you need to approach the game as a dedicated and fearless player.