What lessons were learned about the diamond necklace in Guy de Maupassant's "The Necklace"?

One of the
lessons learned in 's short story,
"," is that of the dangers of extreme personal
vanity. Madame Loisel was
single-mindedly absorbed with the idea of the ball to which she and
her
husband were invited. It was to be the greatest night of her life, and she was willing
to
allow her husband to spend the family's savings on a gown that she
considered necessary for the
function. Yet, that was not enough. Expensive
accessories were also needed, so she took the step
of borrowing what she
thought was an appropriate necklace for the finishing touch to her
ensemble.
She could not focus on anything beyond the ball--it was to be her greatest
moment.
Ironically, the necklace, which proved to be paste, fooled everyone,
including Mathilde. The
loss of the necklace certainly brought both of the
Loisels back down to earth, yet her own
vanity would not allow her to admit
to the loss of the necklace to its owner. A simple admission
of truth to her
friend would have solved the problem and saved them the years of toil that

followed.