Loss aversion

PrepNuggets

Tendency of investors to dislike a loss more than they like a gain of an equal amount. This theory is used by some to explain why some investors overreact to a fall in share price. 

Don’t confuse this with risk aversion in traditional finance, which is a rational behaviour.   Loss aversion, on the other hand, is irrational as the dissatisfaction from a loss should not outweigh the satisfaction from a gain of the same magnitude.