Here is another piece of trading rule from Paul Tudor Jones, quoted from Market Wizards: Interviews with Top Traders.
The most important rule of trading is to play great defense, not great offense. Every day I assume every position I have is wrong. I know where my stop risk points are going to be. I do that so I can define my maximum possible drawdown. Hopefully, I spend the rest of the day enjoying positions that are going in my direction. If they are going against me, then I have a game plan for getting out.
Don’t be a hero. Don’t have an ego. Always question yourself and your ability. Don’t ever feel that you are very good. The second you do, you are dead.
Jesse Livermore, one of the greatest speculators of all time, reportedly said that, in the long run, you can’t ever win trading markets. That was a devastating quote fro someone like me, just getting into the business. The idea that you can’t beat the markets is a frightening prospect. That is why my guiding philosophy is playing great defense. If you make a good trade, don’t think it is because you have some uncanny foresight. Always maintain your sense of confidence, but keep it in check.