Mark Douglas is one of the key figures in trading psychology and the author of cult-classic books. He was the first to clearly articulate that market success depends less on strategy and more on the trader's mindset. His main thesis is simple yet radical: the market is neutral, it owes you nothing. Fear, greed, hope, and the desire to be "right" are what truly stand in the way of consistent profits. He taught how to embrace uncertainty, think in terms of probabilities, and strictly follow a plan. According to Douglas, a trader doesn't guess the market they systematically execute rules and manage risk while maintaining emotional equilibrium. Mark Douglas's legacy remains relevant today: until a trader gets their head right, no strategy will yield consistent results.