Disposition Effect

The disposition effect is the documented tendency for investors to sell winning positions quickly and hold onto losing positions too long. It's the exact opposite of what works in trading. The phrase "cut losers short and let winners run" exists because the human default is to do the reverse. The psychology behind it is loss aversion mixed with regret aversion. Selling a winner feels safe — you lock in the win, no chance of giving it back. Selling a loser feels terrible — you have to ADMIT you were wrong, which most people will do almost anything to avoid. So they hold the loser hoping it'll come back, while taking the winner off the table. The disposition effect is the single biggest reason retail traders underperform. Even with positive expectancy systems, cutting winners and holding losers turns the math negative. Discipline reverses the instinct: small losers, big winners, even if it feels uncomfortable.