Kahneman and Tversky's prospect theory documented that the pain of losing $100 is roughly twice the pleasure of gaining $100. This is loss aversion.
In trading it manifests as: holding losers too long ('it'll come back'), cutting winners too early ('lock it in'), and over-hedging in ways that destroy edge.
The signature pattern in a journal: average loss > average win, even when win rate is high. R-multiple distribution skews negative. The strategy has expectancy on paper but the execution doesn't capture it.
Awareness alone helps — knowing you'll feel the urge to hold a loser past your stop makes it easier to honor the stop. Rules-based discipline (pre-set stops that the broker enforces, not mental stops) is the standard countermeasure.