Put two rookie traders in front of the screen, provide them with your best high-probability set-up, and for good measure, have each one take the opposite side of the trade. More than likely, both will wind up losing money. However, if you take two pros and have them trade in the opposite direction of each other, quite frequently both traders will wind up making money - despite the seeming contradiction of the premise. What's the difference? What is the most important factor separating the seasoned traders from the amateurs? The answer is money management.Like dieting and working out, money management is something that most traders pay lip service to, but few practice in real life. The reason is simple: just like eating healthy and staying fit, money management can seem like a burdensome, unpleasant activity. It forces traders to constantly monitor their positions and to take necessary losses, and few people like to do that. However, as Figure 1 proves, loss-taking is crucial to long-term trading success.Amount of Equity Lost Amount of Return Necessary to Restore to Original Equity Value 25% 33%50% 100%75% 400%90% 1000%Figure 1 - This table shows just how difficult it is to recover from a debilitating loss.Note that a trader would have to earn 100% on his or her capital - a feat accomplished by less than 1% of traders worldwide - just to break even on an account with a 50% loss. At 75% drawdown, the trader must quadruple his or her account just to bring it back to its original equity - truly a Herculean task!