I believe I copped that quote out of Robert McKee's follow-up treatise to STORY which is called DIALOGUE, and might be better than its predecessor for the purposes ITT. STORY and David Mamet's THREE USES OF A KNIFE are good for the big picture, direction, intention. 3UOTK's understanding drama is monumental to understanding some of the ways people comport themselves but does little for mechanics. With Mamet mechanics, the interesting thing for me is that he writes and rehearses using a metronome, which is why I brought up my preference for cadence earlier. No matter how well dressed or constructed, words are lost if they're not heard clearly.
The Gap. What's more appreciated, but still reviled, in the art world is the Gap, though many fledging artists don't realize the Gap yet. The truth is the more you study a thing the greater your appreciation and knowledge of it, but not commensurately does your ability follow this growth. The Gap sits between your taste (what you know to be good and bad) and your ability (ever evolving). The above graphic helps artists understand their tastes may always exceed their ability; but this is a bit harder to swallow when it comes to words because almost everyone discounts how difficult writing truly is. Everyone uses words everyday, so that familiarity breeds a bit of self-contempt -- and thus the work it takes to achieve your taste level becomes this self-limitation.
It's fucked, and hard to find helpful feedback. But the truth is that while your words may not be perfect, they're probably a lot better than you've given yourself credit, which is yet another gap to overcome. Some people say that a writer is in truth a bunch of people pretending to be one person.