Motivation is what gets you started. Discipline is what keeps you going.
I don't see that argument anywhere in the article -- it seems mostly to be that motivation and discipline serve the same purpose, but discipline is more reliable and better.
But then, I don't see the original article as being worth the electrons used to transmit it, its a rant that neither seems to have any grounding nor seems to have any correspondence with my experience.
I'd say the idea that motivation being very important in getting something started and both motivation and discipline playing important roles in keeping going is true.
"The point is to cut the link between feelings and actions, and do it anyway. You get to feel good and buzzed and energetic and eager afterwards."
So, discipline will kick things off and later you'll have the feelings that should have been generated by motivation.