I suspect that most advice like this DOES depend on personality type, but with enough different people offering their insights, presumably the majority of personality types are covered, if one chooses to read enough motivational literature.
My motivation is progress, most of the time. If I'm not making progress, I'll often switch to some easier task that I know I can get done quickly to get my brain in the right space and make 'getting into the zone' a downhill process.
Sometimes, switching back to whatever task was slowing me down is like going back uphill again, but I often find that I'll usually abandon the easy task because, while doing that, the harder task has been mentally solved (once you stop thinking about a problem, yadda yadda).
Of course, where I generally suffer is in getting all the easy tasks done. Solving a problem is fun. Writing a login page isn't, generally speaking. Making a 'reset your password' form isn't. So all those things often get left by the wayside, and I end up with an awesome project that is completely unsellable because the last 10% goes untouched while I work on something else.