Let’s say you’ve been planning to go see a movie this Friday, and have already bought a ticket, but now that it’s time to go out you realize that you don’t want to go, and that you would rather enjoy spending your evening at home. Should you go or not?

Most of the people say yes, after all, the ticket has already been paid for, and it’s nonrefundable, so you wouldn’t want it to be wasted, right?

That is called a Sunk Cost Fallacy — the ​idea that people tend to stick with the courses of action they have ​invested ​money, ​time, or ​effort in, ​even when continuing is not the best thing to do.

If you think about it, it’s irrational to let the costs that we can’t recover to influence our decisions, only future costs and benefits should matter. But we don’t want to admit our mistakes, to “waste” our investment, so we often stick by our past choices that continue costing us more.

The movie example may not make it seem like a big deal, but this fallacy often leads to more significant consequences. Many people stick with professions they dislike because they have spent that all this money and time on getting their degree. They often don’t consider that starting over is better than being miserable for the rest of your career. Or people stay in unhappy relationships because of all the time they have invested in them.