I had some skepticism from a friend when I told him that graduate school is significantly easier than undergrad. It's not that the work is "easier" in any kind of objective sense, it's that almost by definition if you're going to graduate school it's for a topic that you think is interesting, and as such you're going to have more interest and/or aptitude for it.
I had trouble with university the first time around, but it wasn't for the stuff that I thought was interesting. I did fine in my math classes and physics courses and the like; the thing that I struggled the most with were my "easy" courses (e.g. multicultural film). I just did not care about anything that wasn't math or computers, and as such I had trouble forcing myself to do the homework or study and of course I did poorly in the courses.
I've gotten a lot better at forcing myself to do boring work now, but ironically once I decided to do grad school and get my masters, I found it a lot easier. I didn't have to do any courses that I thought were boring. I got to focus on data structures and math and programming languages. You know, fun stuff! As such the masters was (comparatively speaking) a breeze for me because I didn't mind spending hours studying every day.
It occurs to me, though, that this advice might just be about me specifically, which I suppose is the point of the article.