It's hard to describe the inevitable "inside-the-bubble" mentality one takes on while in graduate school, whether PhD or MA. Not being able to escape that mentality is what makes people quit, I believe. It'd help if people could at once say, "I will be in the bottom third of PhDs in my field" yet work hard nonetheless. Instead, the grad school mentality creates an enveloping sense of insecurity: "Am I smart enough?" is often an obstacle.
And how about reading a minimum of four hours a day, every day, for about ten years? The comment about candidates being true believers in the "life of the mind" is right on. I think I'll use that for my cover letter.