Sunk cost in your own head

Everyone can define the sunk-cost fallacy and almost nobody catches themselves committing it, because from the inside it does not feel like a fallacy. It feels like commitment, or loyalty, or refusing to be a quitter — all things you have been told are virtues.

The sentences are recognisable once you know them. "I have already put two years into this." "If I stop now, all of that was wasted." "It would be a waste of everything I have spent." Each of these makes the past a reason for a future decision, and the past cannot be a reason, because no choice you make now can change it. The money is gone whichever way you decide.

The test that cuts through it: if someone handed you this business today, with its current customers, current revenue and current trajectory, and none of your history in it — would you take it on? If the answer is no, then the only thing keeping you in it is the part that has already gone. A second version, for people who find that too abstract: would you advise a friend in exactly this position to continue? Most people are markedly more honest on behalf of someone else, which is itself worth noticing.