Almost every line of this poem denies what the speaker sees, smells, or feels. Purple light on the mountains isn't dawn, a crushed pile at their feet isn't glass, a dark bruise isn't a scar, and red on the collar isn't blood. Taken together, the images suggest something violent has happened, perhaps to the speaker, though the poem never says so. Instead it keeps explaining the evidence away.
The turn comes at "i am not here / i must not stay," where the speaker seems to be detaching from their own body. Even the broken arm and the reflection are disowned. After that, the denials reach emotions: the water at the throat isn't tears, the panic isn't love, the flash on the snow isn't hope. The line "it is not your business" suggests an outsider has noticed, and is being shut out.
The mood is cold, numb, and quietly desperate. The closing "everything is fine" sounds like a rehearsed lie, and the final "dusk" hints the dawn was never really safe.