Mathilde Loisel, the protagonist, who has beauty, but she doesn't have the lifestyle she wants, throws the invitation her husband gave her to the ball on the table.
It was only worth 500 francs!
She thinks that she has nothing to wear, and that another wife is more deserving of the invitation. Her husband gives her 400 francs for her dress, and they come up with the idea to ask her rich friend Mme. Forestier for jewels, in which she gives her a necklace.
I should have just told her!
She gets to the ball, and has an amazing time. She gets home, and realizes that she has no necklace! Her husband and herself travel to different jewelers, and she pays 40,000 francs, with many loans.
After many years, she has finally paid off all of the loans for the necklace. She is walking through the Champs Élysées, and she sees Mme. Forestier! She decides to tell her about the whole necklace incident, and Mme. Forestier tells her the necklace was paste!
She finds out that the necklace was only really worth 500 francs, and she realizes that she should have just told her friend instead of keeping it a secret all this time!
"Don't make the same mistakes I did! It cost me years of my life! Don't lie, and don't be greedy!"