The speaker describes living a double life: smiling and lying on the outside while keeping the truth locked away. They picture themselves as a piece of glass on the surface, hard and sharp, but soft and cloud-like within. The trouble is that the glass is the only part anyone sees, and the speaker fears it will eventually shatter the real self underneath.
What stands out is how the poem moves from self-protection to loss. If the real self is destroyed, only an empty, drifting shell remains, and because everyone has only ever seen the shell, no one will notice anything is missing. The final lines loop back on themselves: the truth was hidden so well that its disappearance will go unseen.
The mood is lonely, resigned, and quietly frightening. The speaker sounds trapped by their own disguise, aware that the very thing meant to protect them is also what will erase them.