The KEY point there is capital preservation and money management; properly controlling the amount of money you risk per trade (your leverage and exposure to the market) is the primary thing that will make or break you as a trader; in fact, it will decide the fate of your entire trading career. The difference between the two traders is that only one of them may have the mental abilities to manage risk, plan for losses, manage trades and execute capital management correctly and consistently (meaning with discipline over time). Whilst sound capital and risk management is certainly the “key” to success in the markets, combining these money management skills with an effective trading strategy will give you an extremely potent edge in the market.