Concerning the custom of breaking the glass, they found many interpretations. Some of these have already been recounted here on m.lj by others. Breaking a glass recalls the destruction of the Bet Hamikdash, teaching us that even our great joy at a wedding is tempered by our loss of the holy Temple. Breaking a glass reminds us that marriages are fragile, and must be tended with care. Breaking a glass is a subliminal message that weddings transform the participants.
Unmarried people become a married couple, with new responsibilities.
Just as the shards of shattered glass cannot return to their former state, the wedding participants are forever changed. Breaking a glass is like a chick shattering its egg to emerge into a new world and a new phase of life. Breaking a glass symbolically recalls rupturing the hymen. Though this is never given as an official interpretation, and hardly anybody ever says this explicitly during a wedding ceremony, still the symbolic identification is difficult to deny. The symbolism is kept at a subconscious level.