A hungry fox once saw some sweet grapes hanging from a vine that was trained along a high trellis.
"I want those grapes," he said to himself.
So he jumped for them.
He did not get them.
He jumped again.
Still he did not get them.
He jumped again and again. They were too high.
At last he gave it up and went away.
"I don't want those grapes," he said.
"They are sour grapes. I know they are sour. They are not fit to eat."