Lyric discussion by sinistercontrivance 

Cover art for Last lyrics by Nine Inch Nails

I think it's about losing yourself, and desperately clawing up to recover from a frenetically paced downward spiral. Thats the more general theme. Specifically this song is about attempting to sustain yourself through carnality when you have lost so much.

This song, as a special place in my heart, so to speak. I've been exactly where it describes.