The "breaking of the glass" refers to a traditional Jewish custom during weddings, where the groom shatters a glass, often wrapped in a cloth, at the end of the ceremony. This act symbolizes the fragility of relationships and serves as a reminder of the destruction of the Second Temple in Jerusalem. The sound of the glass breaking also brings joy to the celebration, as guests often shout "Mazel Tov!" which means "good luck" or "congratulations." This ritual highlights the balance of joy and sorrow in life, emphasizing that happiness can coexist with sadness.