LOOKING FOR POEM, maybe called "Sleep"

I'm looking for a poem I read years ago in an anthology of 20th century American poetry. I think it's called "Sleep". In any case, that's what it's about. It has a steady repetitive rhythm, and the last lines go something like this: "You rise to the edge of your despair/ You fall, and then you sleep". Not much to go on, I know, but if anyone happens to recognize this poem and can help me find the name of the poet and the poem as a whole, I'd be very grateful. Thank you.