What Makes a Kid Happy?

If a child does something good, and if you tell the kid it did something good. For example, let's say i have a child, and my child just learned how to ride a pike. What would i do? I'ld congratulate him, and i would present him with a prize. And the prize would make him happy. But when these kids grow up to be adults, they wind up like you because there is no external party that is now rewarding you for accomplishment. So then you end up accomplishing without being happy.