Business and Economic textbooks warn against committing the Sunk Cost Fallacy: you, rationally, shouldn't let unrecoverable costs influence your current decisions. In this paper, I argue that this isn't, in general, correct. Sometimes it's perfectly reasonable to wish to carry on with a project because of the resources you've already sunk into it. The reason? Given that we're social creatures, it's not unreasonable to care about wanting to act in such a way so that a plausible story can be told (...) about you according to which your diachronic behavior doesn't reveal that you've suffered, what I will call, diachronic misfortune. Acting so as to hide that you've suffered diachronic misfortune involves striving to make yourself easily understood while disguising any shortcomings that might damage your reputation as a desirable teammate. And making yourself easily understood to others while hiding your flaws will, sometimes, put pressure on you to honor sunk costs. (shrink)