Kostolany's Ten Commandments & Ten Laws

In The Confession of a Speculator, André Kostolany condenses a lifetime of financial market observation into two lists: ten commandments (what not to do) and ten laws (what to do).

Keeping these here as a personal investment reference.

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Ten Commandments — What Not to Do

1. Don't follow tips or hope to hear inside information.
2. Don't believe that sellers know why they're selling, or buyers know why they're buying — that is, don't assume they know more than you do.
3. Don't try to recoup losses.
4. Don't consider past stock prices.
5. Don't sleep on your securities — don't forget about them while waiting for a better price; that is, don't fail to make a decision.
6. Don't constantly watch every small price movement or react to every rumor.
7. Don't continually tally your current gains or losses.
8. Don't sell a stock just because it shows a profit.
9. Don't let political opinions color your judgment.
10. When you profit, don't become arrogant.

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Ten Laws — What You Must Do

1. Have an idea and think it through before acting: should you buy? If yes, where, which industry, which country?
2. Have sufficient capital so you are never under pressure.
3. Be patient — because first, things never turn out as expected, and second, they turn out differently than you think.
4. If you believe in your own judgment, you must be stubborn.
5. Be flexible and always consider the possibility that your idea is wrong.
6. If you see a new situation emerging, sell.
7. Review your holdings periodically and ask which ones you would buy today.
8. Only buy when you see a major growth prospect ahead.
9. Consider all risks, even the most unlikely — always account for uncertainty.
10. Even when proven right, remain humble.