Yes. I keep getting that feeling everyday with my work as of now. And I also got a PhD after fighting a lot of hardship including huge opposition from my parents to the effect of having lost contact with them. But what you said does ring a bell in that, I need to be constantly doing my work in getting that feeling. (apart from my PhD which every once in a while makes me go wheeeee).

I guess with kids, its like my PhD but a constant source instead of static fading in time?