Sunk costs are the investments that you’ve put into something that you can’t get back out. They are the years you spent training for a profession you hate, or waiting for your commitment-phobic boyfriend to propose. They are the thousands of dollars you spent on redecorating your living room, only to find that you hate living in it. Once you’ve realized that you probably won’t succeed, or that you are unhappy with the results, it shouldn’t matter how much time and effort you’ve already put into something. If your job or your boyfriend have taken up some of the best years of your life, it doesn’t make sense to let them use up the years you’ve got left. An ugly living room is an ugly living room, no matter how much money you spent making it so.
As studies by behavioral economists like Daniel Kahnemen and Dan Ariely show, people are generally loss-averse. Putting in a lot, only to end up with nothing to show for it, is just too awful for most of us to seriously consider. The problem is one of focus. We worry far too much about what we’ll lose if we just move on, instead of focusing on the costs of not moving on: more wasted time and effort, more unhappiness, and more missed opportunities.