In Victor Hugo's "Les Miserables," the quote emphasizes the importance of reflecting on the past. It suggests that a head that fails to look back at lost horizons is devoid of both thought and love. This implies that contemplation of previous experiences is essential for understanding oneself and forming meaningful relationships. Without this reflection, individuals can become stagnant, unable to grow or connect with others in a profound way.

The message highlights that our thoughts and emotions are intricately linked to our past. Acknowledging and learning from what has been lost is crucial for personal development. Hugo urges readers to embrace their history, as it shapes their identity and capacity for love. In essence, true wisdom and emotional richness stem from an awareness of the journeys we've taken and the lessons they impart.