Sunk Cost Fallacy

“The sunk cost fallacy is most dangerous when we have invested a lot of time, money, energy, or love in something. This investment becomes a reason to carry on, even if we are dealing with a lost cause. The more we invest, the greater the sunk costs are, and the greater the urge to continue becomes.
Investors frequently fall victim to the sunk cost fallacy. Often they base their trading decisions on acquisition prices. “I lost so much money with this stock, I can’t sell it now,” they say. This is irrational. The acquisition price should play no role. What counts is the stock’s future performance. Ironically, the more money a share loses, the more investors tend to stick by it.”

Excerpt From: Rolf Dobelli. “The Art of Thinking Clearly.”