What is the moral of the story in The Necklace by Guy de Maupassant?

There are
a number of different morals one could derive from "." It's just one of the reasons
why it's such a fascinating story. First of all, and perhaps most obviously, the story teaches
us that material things cannot bring happiness. Wearing what she thinks is a valuable necklace,
Mathilde feels like the belle of the Education Ministry ball. But her happiness doesn't last for
very long, and indeed her shallowness and obsession with material objects leads to great
unhappiness. "All that glitters is not gold" is an appropriate description both of the
fake necklace and the high society life that Mathilde briefly tastes and to which she
desperately aspires.

Related to the first point is the theme of class
snobbery. Mathilde acts like she has noble blood coursing through her veins, despite her lower
middle-class status. And it's Mathilde's desire for social climbing that ultimately leads to her
undoing. The moral appears to be that class is something you're born with, not something to
which you can, or should, aspire. Wanting so badly to be a member of a supposedly higher social
class means that you're trying to be something and someone you're not. This doesn't necessarily
mean that people shouldn't try to improve their position in life; but what it does mean is that
they should remain true to themselves, instead of engaging in fantasies and delusions, imagining
themselves to be different than they really are.