answer:I don’t think that “deep dissatisfaction” is a driver; rather, people learn because of interest and curiosity. And expertise arises from continued curiosity about a subject. Indeed, a deep satisfaction from learning a little and wanting to to know a little more makes one continue studying a subject. Passion, expertise, and self satisfaction are all different. I am a cyclist, and through the nineties I was quite passionate about it. And I knew I would never be a racer, and that I would never even be the strongest on club rides. Yet I was quite satisfied with my ability and my stamina. And I did have quite a bit of expertise on cycling, enough to advise people on what kind of bike to buy, getting in shape for long distance rides, how to be safe while riding. I’ve had similar passion and expertise in a number of areas. And I have been satisfied too! It’s not that “each goal is never enough,” Achieving a goal is a bit of a high, and the person wants that high again. And the question discounts anything to do with humility. Consider Derek Jeter. He is as passionate as anyone, definitely has expertise, and I would say for the most part he has had great satisfaction. But he is retiring, not because he is satisfied, but because he is humble enough to know it is time to go, that his body can’t do what it did ten years ago.