Here is a short exchange from the play, Death of a Salesman by Arthur Miller:
Charley: When a deposit bottle is broken, you don't get your nickel back.
Willy: That's easy enough for you to say.
Charley: That ain't easy for me to say.
Charley is telling Willy to recognize that he can't change the past, but Willy holds onto his dreams for himself and for his son, Biff. Charley tells Willy, "Let him go," referring to Biff. And then Charley acknowledges that it is difficult to give up on past dreams.
It's like the old adage, "Don't cry over spilt milk." You can't undo the spill. You can rue the loss, you can clean up the mess, you can buy more milk, you can even learn to be more careful in the future; but you cannot get the milk back.
It's an example of the sunk cost fallacy that we talk so much about in economics: Costs should be based on forward-looking decisions if people are rational maximizers.
For example, what if I paid $12000 for a used car but then realized I don't like it. What I paid for it is irrelevant. The only things I should consider are my options for the future: should I donate the car to charity to get a tax write-off? should I sell it to someone else? etc. Trying to recover my $12000 is meaningless. Instead, I should look forward, identify my options, and choose from among them.
Humans don't seem to work that way though. Willy can't or won't give up on his dreams; he can't give up on the expectations created in the past. And Charley asknowledges that he, too, had trouble giving up the past and making decisions for the future when he says, "It ain't easy for me to say."
Here is another example of the sunk cost fallacy, from this site.
Hal Arkes and Catehrine Blumer ... asked subjects to assume they had spent $100 on a ticket for a ski trip in Michigan, but soon after found a better ski trip in Wisconsin for $50 and bought a ticket for this trip too. They then asked the people in the study to imagine they learned the two trips overlapped and the tickets couldn’t be refunded or resold. Which one do you think they chose, the $100 good vacation, or the $50 great one?
If, indeed, you think the Wisconsin ski trip would be better (of course you don't know for sure, and so the decision will be based on your expectations), then what you paid should not affect your decision because you will not be able to obtain a refund on either trip. You have paid $150 in total; it's gone, it's sunk. The only relevant questions is, "Now what're you gonna do?"
A "rational" maximizer [homo economicus?] would choose the Wisconsin trip, expecting it to be better. What was paid for the two trips is sunk; the decision should be based on expectations concerning future alternatives.
The example continues,
Over half of the people in the study went with the more expensive [Michigan] trip. It may not have promised to be as fun, but the loss seemed greater. That’s the fallacy at work, because the money is gone no matter what. You can’t get it back. The fallacy prevents you from realizing the best choice is to do whatever promises the better experience in the future, not which negates the feeling of loss in the past.
Willy does this throughout the play. He maintains his dream of being a big-time salesman even though, "He was a happy man with a batch of cement," and would have been much more successful in the construction business. He not only refuses to recognize his own, personal comparative advantage, but he holds onto that dream even in the face of his apparent lack of success. Does Linda do the same thing when she talks him out of moving the family to Alaska? Maybe, or maybe she just has different expectations.
Willy's dreams for himself, for Biff, and for their relationship are like a sunk cost. He could give up the dreams and be more successful, but he doesn't let go of them. Instead of looking forward and making decisions based on his options for the future, Willy keeps looking backward, trying to live a dream that cannot be, even in end.
Note: I play Charley in the upcoming performance of Death of a Salesman at Procunier Hall, The Palace Theatre, London, Ontario.