In Aesop's Fable of "Tthe Fox and the Grapes," we learn that the fox wants a cluster of grapes hanging from a trees. He tries over and over to jump high enough to reach for them, with no success.
This fable has been "covered" by several writers after it was presented as a part of Aesop's Fables.
First of all, a fable is a very small "story" (either presented as prose—straight writing—or verse, also known as poetry) which includes:
These creatures or things are personified. When this happens, the subject of the personfication is said to be "anthropomorphized" which is when human qualities are given to non-human things. The fable includes a moral (as in "moral to the story") which is the statement of a "life-truth." The moral of the story may then be presented in a "pithy maxim." In "The Tortoise and the Hare," the moral is: slow and steady wins the race.
For "The Fox and the Grapes," we learn that the fox being very hungry has tried in vain to reach the grapes. When he gives up in failure, he comments, "I don't need any sour grapes," he is basically trying to say that his failure means nothing since the grapes weren't worth the effort anyway. (This is probably where the description of someone being "sour grapes" comes from.)
The fox is hard-working to an extent. He uses all his strength to jump as high as he can. He is perhaps not very realistic as the fruit is too far off of the ground, but we can admire his attempts. However, his attitude is rather negative at the end. Because he is unsuccessful, rather than acknowleding his inability to reach his goal, he redirect our attention away from himself, noting not his failure, but the fact that the grapes are probably not worth the effort and that he is better off. There is no validation in that statement, so he is simply making excuses.
In Jean de La Fontaine's version of the fable, the fox's last line has an ironic twist—and a pun:
"Better, I think, than an embittered whine".
(Note how "whine" is used, as opposed to "wine" which comes from grapes.) Another author, Phaedrus, writes this closing line—the fable's maxim:
People who speak disparagingly of things that they cannot attain would do well to apply this story to themselves.
The fox is like many children who want to borrow someone's toy or play in a game, and they are not allowed; their comment is something like, "Well, I didn't want to play in that dumb old game anyway." And this is the fox: childish, with a need to put down something he cannot have.