1. A unprofessional trader cannot make much money, even he understands many things. Because small little detail kills. For example, the lot size of option trading, and the discount caused by liquidity of ETF.
2. Trading can be very distractive. It is costly to human capital.
3. Never use money that you will need in 5 years to trade. It creates fear, and fear makes you a poor trader.
4. Never use more than 10% of your wealth to trade. It creates fear, and fear makes you a poor trader.
5. Never use leverage.