"It reminded me of this proverb I was told a lot as a kid: As a dog returns to his vomit, so does a fool return to his folly. You can be very aware of how crazy you’re being sometimes, and be very aware of how you’re not able to help yourself."
He had some more stuff to say about the song too...
Chris explained the title "Vomit" in this interview, as well as the rest of the songs on the album: http://www.theatlantic.com/entertainment/archive/2011/09/the-story-behind-the-loveliest-rock-album-of-the-year-so-far/245138/
"It reminded me of this proverb I was told a lot as a kid: As a dog returns to his vomit, so does a fool return to his folly. You can be very aware of how crazy you’re being sometimes, and be very aware of how you’re not able to help yourself."
He had some more stuff to say about the song too...