For the same reason that most businesses fail slowly (by focusing on small details instead of big-picture stuff), most writers can’t get their work better than a certain level of passable mediocrity because they’re “optimizing” the small stuff before they hit on a project that’s worth optimizing. They approach revision by thinking about word choice and commas and cuts and line breaks, but those things can only make a poem or a novel or whatever 1-5% better. A radical revision that completely rethinks the scope or the flow or what have you could make it twice as good.

—Elisa Gabbert