Austin Kleon posted this gem about punk artists defining their work by negatives, with a nice quote from David Byrne on how the Talking Heads set out not to do certain things other bands had done. "The only sensible course was to avoid all of it, to strip everything back and see what was left. ...It was mathematics; when you subtract all that unwanted stuff from something, art or music, what do you have left?" Byrne adds that he later moved beyond that approach, "but the dogma provided a place to start."
In a Chicago rock discussion group, someone posted Paul Westerberg's interview with Musician, in which he discusses how artists define themselves in relation to others, whether they're aspiring to be in the in-group or to break away: "It takes a lot of courage to be different but it takes a great deal of hard work to be the same. I think in the end you get the same result but you've got to be what you are." (I've always had the impression that Westerberg had little choice about being different; he's constitutionally perverse. In Trouble Boys he says that if you tell him "White sheet rain," he'll come back with "Black blanket sun.")
What do those things mean for the song? for me as a person? Defining by absence is useful, but there's a point at which it becomes too reductive. What isn't starts to obscure what is and what can be. I was stuck on a refrain of "I won't think about you, I won't think about you" until I figured out that it needed to break so the song could become a whole song, not just an idea. Ultimately the no isn't enough; you need the yes too. Or I do.