This was my exact path. For the longest time, the goal was to become gainfully employed as an engineer. Achieving your primary goals seems to be a lot like meeting your heros - you'll always be disappointed. Once I had the job, then I had to figure out how to keep it from completely absorbing me.

Most of the stages you mentioned above use an external criteria for success and for motivation. If that's the only kind of system you're familiar with, then you probably hadn't had the chance to stop and think "Does doing this make me happy?" because in those systems that question is irrelevant. You do what needs to be done to achieve the grade/rating/performance review and then ask what hoop you need to jump through next.

It seems the people that build truly rewarding careers are generally more internally motivated and because they have a better idea of who they are and what drives and motivates them are in a better position to to say "no" to things.