The moral of "The Necklace" is that we should be grateful for what we have rather than constantly seeking to acquire more. Mathilde Loisel is married to a man with a good job in the Ministry of Education; she has a servant girl who helps her with housework, and her husband is happy with their modest life and exclaims "delightedly" when presented with even simple dinners. However, Madame Loisel is miserable because she does not have fancy clothes or expensive jewels, "and these were the only things she loved." She wants to be "desired" and "sought after" and to charm other people with how "wildly attractive" she is.

Madame Loisel is unable to find happiness, or even contentment, with all that she has, and so she tries to create a night in which she can pretend that she lives the life to which she believes she is entitled. She gets a new dress, goes to a fancy party, and borrows a lavish diamond necklace to wear. Mathilde fails to appreciate a husband who has worked to secure an invitation and who has offered her money (which he was saving for himself) so that she can get a dress to wear for one night, and this ultimately gets her into trouble. She could have been satisfied with her life, but she was not. She could have been happy with her dress, but she was not. She had to have jewels, too, though flowers would have done just as well. If she had been grateful for what she had and not sought to have more, then she could have lived happily and contentedly with her loving husband.

There are several morals to the story "The Necklace" by Guy de Maupassant, which include the importance of being grateful for what you have in life and the dangers of valuing material items. However, the main moral of the story can best be summed up by the well-known aphorism, "all that glitters is not gold."

Mathilde Loisel attaches importance to exterior beauty and is primarily concerned with her physical appearance and social status. Everything Mathilde values is shallow and superficial. She fails to appreciate her comfortable lifestyle and is not grateful for her husband's selfless personality. Instead, Mathilde dreams of being in the upper class and insists on having the most exquisite material possessions.

Mathilde's obsession with exterior beauty and physical appearance motivates her to borrow Madame Forestier's necklace. She fails to realize that the necklace is made from imitation diamonds and sacrifices everything she has to replace it after losing it. Mathilde attaches too much value to appearances and wastes a significant portion of her life paying the price for her mistake. She is deceived by the necklace's appearance and believes that she has lost an expensive piece of jewelry. If Mathilde would have exercised perspective, recognized that "all that glitters is not gold," and appreciated things with inherent value, she would not have wasted ten years of her life and lost her beauty.

There are a number of important moral lessons in "The Necklace" but I'd argue that the most important one of all is that you should always be true to yourself. Madame Loisel certainly isn't and therein lies her downfall. She leads a perfectly comfortable, respectable life—she's a good deal better off than most people in France at the time—and yet she's still not happy with her lot.

Her main problem is that she has delusions of grandeur, thinking herself to be better than she really is. Mathilde's fantasies of living the good life eventually lead to a grim existence of mindless drudgery and grinding poverty. If she'd been grateful for what she had then this wouldn't happened. There's nothing wrong with being ambitious in life, and perhaps Monsieur Loisel can be criticized on this score, but that doesn't mean pretending to be something you're not. Mathilde acts like a princess, thinking she's entitled to better things. But she's simply deluding herself, and the results of her delusions are disastrous for her and her husband.

If one had to sum up the moral of the story in a saying, then perhaps we should give the last word to Polonius, in act 1, scene 3 of Hamlet:

This above all: to thine own self be true,
And it must follow, as the night the day,
Thou canst not then be false to any man.

Guy de Maupassant's short story "The Necklace" is about a young woman, Madame Loisel, who daydreams about wealth, social status and luxury. When she is able to live her preferred life for one night at a fancy ball, adorned with a new dress and a seemingly expensive necklace, she is truly happy. With the loss of the necklace, a symbol of wealth and material status, her life is forever changed as she is thrown into poverty. In the end, we learn the necklace was actually worthless, proving her original mindset wrong. 

A saying that sums up the moral of the story might be: Be satisfied and grateful for the things you have rather than striving for things that may appear better but often are not.

In the beginning of the story, while Madame Loisel is daydreaming, the reader learns she lives comfortably. After all, she has a maid. She also has a husband who is obviously devoted to her. Realizing she is bored, he tries to brighten her life by bringing home an invitation to the fancy ball and he even uses some of his savings to buy her a new dress. She doesn't appreciate what she already has and foolishly loses the necklace as she hurries away from the ball. The loss of the necklace causes her to lose her youth, her beauty and her dignity. Her life would have been better had she been satisfied with what she already had.