I'm curious, though -- does anyone think that one attitude is better than the other? Or is it just a matter of individual preference? Job-as-income-stream, or career-as-personal-identity?

I think there's an argument to be made that the first attitude (personal identity) is instrumentally superior (even as it may well be epistemically inferior). Someone whose identity is wrapped up in their job may work far harder at their job and so eventually gain greater skills or produce better work in their chosen profession than the person who strives for the same results but as a hobby and works in another field. It's hard to have two masters.

For example, think about rock stars or pro sports. Objectively, epistemically, these are absolutely lousy careers. Tiny chance of success and even the mega-hits don't do so well. Not to mention all the issues like dying prematurely, which seem to be intrinsic to the careers. (See the recent New Yorker about NFL cutting a few decades off its players' lifespans, or look at probably the wealthiest musician ever - Michael Jackson.) But if you believed this, you're never going to become a rock star.

A would-be rationalist rock star is like the two-boxing decision theorist faced with Newcomb's Problem. 'Oh, if only I could brainwash myself to take one box! Then I would be much wealthier.'

Or so the argument would go.