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 they 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.