In Victor Hugo's "Les Miserables," the observation is made that unhappiness teaches children to become silent and withdrawn. This idea suggests that when children face hardships and struggles, they often learn to suppress their emotions and voices. Instead of expressing their feelings or seeking help, they retreat into silence, a defense mechanism against their pain.

The quote reflects a broader theme in the novel about the impact of societal issues on the innocence of youth. It highlights how suffering can stifle a child's spirit, forcing them to endure their struggles in isolation, which can have lasting effects on their development and well-being.