Have you ever felt stuck in a relationship that went sour but you just couldn’t bring yourself to end it? It’s not just you. It happens to a lot of people in a lot of situations.

There’s even a term for it: the sunk cost effect. Once we’ve invested time, money or energy into something, we’re hesitant to give up on it.

It’s the reason we have closets full of clothes we no longer wear, stay in jobs we no longer like and are reluctant to move out of places we used to love but now drive us crazy.

A paper published in the journal Psychological Science explores our tendency to stay all in on a botched plan.

“The sunk cost effect is the general tendency for people to continue an endeavor, or continue consuming or pursuing an option, if they’ve invested time or money or some resource in it,” said Christopher Olivola, an assistant professor of marketing at Carnegie Mellon’s Tepper School of Business. “That effect becomes a fallacy if it’s pushing you to do things that are making you unhappy or worse off.”

One of the reasons we get snared in this psychological trap may be because we hate experiencing regret and admitting that we have made a mistake, experts suggest. Sticking with the plan, even when it no longer works, is a way to avoid cognitive dissonance: the mental disconnect between paying for something and not getting the expected return on investment, Olivola said.

“After we commit, we humans tend to shackle ourselves to our own decisions,” an article in Smithsonian Magazine put it. The sunk cost fallacy might be a self-defense mechanism, a way to reinforce our confidence in the effort we’ve put in — basically, a way to save face with ourselves, as University of Minnesota neuroscientist Brian Sweis told Smithsonian.

Bad romance is an iconic example. Sometimes people chain themselves to an unhappy relationship just because they’ve wasted so much time on it. If they cut and run, they will have to face the failure. “The longer you’ve been together, the harder it is to break up,” Olivola said.

This tendency to stick with the plan, even when it’s a total bomb, also appears to happen in other species, such as mice and rats. □