This is a quote by Lelouch from the anime Code Geass: Rebellion 2 (I can't remember if it is the subbed or dubbed version)

A long time ago, Nunally, Suzaku, and I talked about something. We wondered what happiness would look like if we could give it a physical form. If I'm not mistaken, I think it was Suzaku that said that the shape of happiness might resemble glass. His reasoning made sense. He said that even though you don't usually notice it, its still definitely there. You merely have to change your point of view slightly, and then that glass will sparkle when it reflects the light. I doubt that anything else could argue its own existence more eloquently.