Once their was a fox who’s thirsty. He walked and walked until he saw a bunch of grapes. Because he was thirsty, he jump and jump but it is useless because the grape is too high tthat he dont even touch it. Until he was tired but he dont give up, he jump many times until he realize that the grape is sour even if he dont even touch nor taste them.
He was actually just sour graping because he cant eat the grape. So he put in his mind that it is sour.