Originally Posted by Wikipedia: "Cognitive dissonance"
Examples
A classical illustration of cognitive dissonance is expressed in the fable The Fox and the Grapes by Aesop (ca. 620–564 BCE). In the story, a fox sees some high-hanging grapes and wishes to eat them. When the fox is unable to think of a way to reach them, he decides that the grapes are probably not worth eating, with the justification the grapes probably are not ripe or that they are sour (hence "sour grapes"). This example follows a pattern: one desires something, finds it unattainable, and reduces one's dissonance by criticizing it. Jon Elster calls this pattern "adaptive preference formation".[6]