Sour grapes
English Idiom
Meaning: When someone disparages something they cannot have, they belittle it to make themselves feel better. This behavior is often a defense mechanism to cope with disappointment.
Origin: The idiom 'sour grapes' originates from Aesop's fable 'The Fox and the Grapes.' In the story, a fox tries to reach a bunch of grapes hanging high on a vine. After several failed attempts, the fox gives up and walks away, muttering that the grapes were probably sour anyway. This tale perfectly illustrates the human tendency to devalue what one cannot attain.
