THESE GRAPES ARE SOUR
This proverb has its origin from the fable, Fox and the Grapes. Once a fox tried to get a bunch of grapes beyond his reach. Even after several leaps he failed to get it. Then the fox went off saying that the grapes were so sour that he did not want it. Here, the fox made several efforts to get the grapes. But it failed.
We can see a lot of examples around us in which people after failing to get what they desire, often term those things as worthless. Such scorn comes only after failure. Certainly that is a face saving exercise; this often makes the failure bitter and shameful.