Gambler's Fallacy
Risk ManagementThe belief that a market move or trade outcome is ‘due’ after a streak — a common reason traders raise size after losses.
The gambler's fallacy, also known as the Monte Carlo fallacy, is the belief that an independent outcome becomes ‘due’ after a streak — that a currency pair must bounce because it has fallen for five sessions, or that a losing run makes the next trade more likely to win. Individual trade results are not drawn from a fixed deck that has to balance out; whatever edge a strategy has is a property of the whole sample, not a debt the market repays. The fallacy matters mainly because it invites larger positions after losses, which is the logic behind martingale-style systems and a common route to a rapid drawdown. Treating each trade as an independent decision, sized by a fixed rule, is the usual defense.