I disagree with a little bit of her phrasing--I think refining mistakes to smaller and smaller mistakes does constitute 'getting better'--but I think she's dead-on when she says (more or less) that there is not perfection in art, just smaller and smaller margins of error. And I think she's nailed down a a common reason for the well-documented phenomenon of neopro flameout; writers who sell a little start assuming they are 'good enough,' when there is in fact no such thing.
What's important, I think, is to keep striving for the flawless story while acknowledging on some level that there is no such thing.
Writers are like sharks. If we stop swimming, we die..