The cause of Matilda's ruin was her own dissatisfaction with her life and her desire for luxuries she could not afford. Born into a family of clerks, she suffered incessantly feeling she was born for all delicacies and luxuries. The poverty of her apartment, the shabby walls and worn chairs tortured her. Her ruin was ultimately triggered when she borrowed a necklace from Mme Forestier to wear to a grand party and then lost it, which changed the entire course of the Loisels' life.

Matilda could have avoided her ruin in several ways. First, she could have been content with her life and accepted her circumstances instead of constantly suffering over what she lacked. Second, she could have attended the party without borrowing jewellery, as her husband suggested the dress she already had seemed very pretty. Most importantly, she could have confessed to Mme Forestier that she had lost the necklace instead of hiding the truth, which would have revealed that the necklace was not as expensive as she assumed and saved her from years of suffering.