Mental accounting is the cognitive bias of treating money differently based on its source, intended use, or the mental 'account' it is assigned to — even though all money is fungible. In trading, this manifests as treating profits differently from initial capital (risking 'house money' more freely), segregating portfolio performance by position rather than total, or taking excessive risk with bonus or windfall funds.
House money effect: treating profits as less valuable than initial capital and risking them more freely. Segregation: evaluating individual trades in isolation rather than as part of a total portfolio. Windfall effect: treating unexpected gains (airdrops, bonuses) as 'free money' and risking them recklessly. Loss compartmentalisation: ignoring unrealised losses by not 'counting' them. All capital has equal value regardless of its origin.
Apply the same position-sizing rules to all capital regardless of whether it came from profits, deposits, or windfalls. Evaluate every new trade based on current total portfolio value, not on a mental sub-account. Ask: 'Would I take this same risk if this money came from my savings rather than from trading profits?' Treat all funds with equal respect in your risk-management framework.
Review your total portfolio performance, not individual position P&L, to maintain perspective. Use the same stop-loss discipline on profitable accounts as on new accounts. Close losing positions based on technical criteria, not on whether the loss is 'realised' or 'unrealised'. Reconcile all accounts regularly to prevent mental segregation.
Applicable during portfolio management, position sizing, and risk assessment at all times
The house money effect is one of the most dangerous biases in trading — traders who double their account often blow up shortly after because they begin treating profits as 'free money'. Force yourself to re-anchor after significant wins: the new, higher account balance IS your capital, and it deserves the same protection. Use a single, unified risk-management framework for every pound or dollar in your account.
The sunk cost fallacy occurs when traders continue holding a losing position or investing additional capital because of the resources already committed, rather than evaluating the position on its current merits and future prospects. The time, money, and emotional energy already spent become anchors that prevent rational decision-making, leading to escalating commitment to failing trades.
Confirmation bias is the tendency to search for, interpret, and remember information that confirms your existing beliefs while ignoring contradictory evidence. In trading, this means once you form a bullish or bearish view, you unconsciously filter information to support your position — ignoring warning signs and overweighting supportive data.
Hindsight bias is the tendency to believe, after an event has occurred, that you predicted or expected the outcome all along. In trading, this manifests as reviewing charts after the fact and feeling certain that the signals were obvious, leading to overconfidence in future predictions and an underestimation of real-time uncertainty. This bias distorts trade journaling and prevents genuine learning from both wins and losses.
FOMO (Fear Of Missing Out) drives traders to enter positions impulsively because they see prices rising or because social media is buzzing about an asset. Herding behaviour — following the crowd — amplifies FOMO by creating social proof. Together, these biases cause buying at tops and chasing momentum that's already exhausted.