The speaker is getting ready for something rough, and the poem is mostly about how unprepared, and how breakable, they feel. A chest of glass is a vivid image of vulnerability: one hard jolt and it could shatter. The title, "White fragility," seems to sharpen that idea, though the poem doesn't spell out what kind of fragility it means, so that part is open to interpretation.
The strange details pile up. The speaker's hand is "leased from a pretty lady," as if even their own body isn't fully theirs, only borrowed and temporary. Their head is made of paper, thin and easily marked, and it's "so full of sin" that it tips into vision: they begin to see God. That last line is the surprise. Guilt and fragility don't lead to despair here but to something like revelation.
The mood is uneasy and darkly funny, a mix of nervousness, self-mockery, and a flicker of awe.