The sunk-cost fallacy leads to all sorts of poor decision-making -- like staying too long at a bad job or refusing to drop out of a hopeless mayoral campaign. Here's how Dubner explained it in our podcast on quitting:
A “sunk cost” is just what it sounds like: time or money you’ve already spent. The sunk-cost fallacy is when you tell yourself that you can’t quit because of all that time or money you spent. We shouldn’t fall for this fallacy, but we do it all the time.
But there's new hope for all you sunk-cost believers out there: new research (abstract; PDF) from Andrew C. Hafenbrack, Zoe Kinias, and Sigal Barsade shows that a 15-minute mindfulness meditation practice can help.