Loss aversion
Etymology
From "loss" (Old English "los," destruction) and "aversion" (Latin "aversio," a turning away). It was established as a technical term by psychologists Daniel Kahneman and Amos Tversky in their 1979 work on prospect theory, which found losses loom roughly twice as large as gains.
noun phrase · /LOSS uh-VUR-zhun/
The tendency to feel the pain of a loss more intensely than the pleasure of an equivalent gain.
What it names
Explains why we cling to what we have and take odd risks to avoid losses — losing $100 hurts more than finding $100 delights.
Example
Loss aversion kept him in a plunging stock — selling would make the paper loss painfully real.
Related idea
The sunk cost fallacy is loss aversion in motion over time: we keep pouring resources into a failing venture rather than accept what we’ve already lost.