I'd (and let me start with "I" too) say, it's kind of reflecting one of these rare but wonderful days when everything is running smoothly, and you are in a constant flow of things.
So, here, in this song, it is most likely about someone, a writer?, experiencing a creative flow that is driving him or her forward, probably after a writer's block, and now s/he doesn't need any extra fuel (coffee, pills, etc) to rev up the engine and keep it going.
The "it" would be the creative energy found again.
One inconsistency remains though, which is the quotation, "We've never really been away". Makes me wonder who "we" is, the inner voices that drive the creative process forward? After all, it's or they are something that s/he had thought she lost forever, but now, that s/he decided not to waste any energy on fighting the arseholes any longer, the inner creative source is bubbling again freely.