These faults can be found in many traders and investors: Do not be careless or reckless with your trading. You trade for profit, not for fun and games. Do not be timid; once you have identified an opportunity, attack it. Act on it. Do not get angry over a losing trade and swear to get even. You won’t. Do not get down on yourself for a losing trade, or even a string of losing trades. Find out what you are doing wrong and correct the problem. Do not fall in love with a stock, a bond, or anything else. You must learn that this is conflict, and you must be rather mercenary with your trading and investing.
– Dean Lundell, Sun Tzu’s Art of War for Traders and Investors