I think this article makes a valid point, but manages to miss the bigger picture. It's true, you should love what you do. You should want whatever it is you're going after. BUT (and this is a big but), what you're going after isn't always going to be lovable. In fact, sometimes you'll downright hate it.
The problem with achievement in any endeavor is that people assume it should FEEL easy. They assume that their lack of enthusiasm at any given moment is an indication that something is wrong.
The writer who has writer's block is apt to tell himself he's a fraud.
The guy who's had a fight with his girlfriend might be inclined to question the relationship.
The entrepreneur who's business is on the rocks might wonder if a cubicle job is a better idea.
The beginning programmer who struggles with the concepts might wonder if he's smart enough.
In the face of obstacles, it becomes very easy to question our path. The difference between success and failure in many cases is, i think, the knowledge and wisdom to understand that anything worth doing or having is HARD. It isn't all tea and roses. Sometimes you're going to want to give up and that's ok. That's what SHOULD happen, because if what you're doing is so easy that it never challenges you, then you're likely not doing anything amazing. True motivation is seeing the end game and still having the balls to slog through the miles of crap to get there.