This is called the sunk cost effect.
A sunk cost is time, money, or effort you already spent and cannot recover.
Logically, that cost should not determine what you do next.
Emotionally, walking away can feel like admitting the earlier investment was wasted.
The past cost cannot be recovered
Suppose you buy a ticket to a terrible movie.
After an hour, you are miserable.
Leaving will not return the ticket price.
The money is gone whether you stay or leave.
The best decision should depend on whether the next hour is worth your time.
Why do people stay anyway?
Because leaving can feel like making the earlier cost meaningless.
“If I leave now, I wasted the money.”
But staying does not recover the money.
It only adds another cost: another hour of your life.
Where does this show up?
Projects.
Investments.
Relationships.
Subscriptions.
Repairs.
People may keep adding resources to something because they have already invested so much.
The earlier investment becomes an argument for making a new investment.
Why is this emotionally difficult?
People want earlier decisions to feel justified.
Walking away can feel like admitting a mistake.
That can threaten pride, identity, or confidence.
So the brain may prefer continuing to acknowledging that the original choice did not work out.
What question helps?
Ask:
“If I had not already spent anything on this, would I choose it now?”
That removes the sunk cost from the decision.
If the answer is no, the earlier money may not deserve another vote.
Does finishing ever make sense?
Of course.
Sometimes the remaining benefit is still worth the remaining cost.
The mistake is not continuing.
The mistake is continuing mainly because of what has already been spent.
The money you already spent is gone.
The real question is whether the next dollar still makes sense.
A related piece of human behavior appears in Why do we value things more once we own them?, where the brain handles another everyday judgment or response.
And that’s the short explanation.
Related explanations: Why do we value things more once we own them?, Why do losses feel worse than gains feel good?, and Why can having more choices make choosing harder?