Dust, damp, and dirty windows: the speaker describes a body that feels neglected and shut away, like a house nobody opens. The "you" in the poem seems to turn the speaker's smell into something stored in a cellar, so the speaker feels kept, almost filed away. Pulling the speaker "down wooden steps" adds to the sense of being led somewhere low and dark.
The ending is the most striking part. Tomorrow comes back only "to look on," as a bystander, while the speaker chooses to "go underground" and become "a hidden floor to lie on." That could mean hiding, giving up, or finding a strange kind of shelter in being out of sight. The poem leaves that unclear, and the uncertainty is part of its power.
The mood is heavy, claustrophobic, and quiet. Short lines and missing punctuation make it feel like whispered thoughts, with no energy left to explain. Yet the speaker's final action sounds deliberate, which gives the poem a faint, uneasy sense of control.