Remember, when you were a kid, you could dance and enjoy it enormously even if you didn't know how to dance?
After you grow out of childhood, you lose that bliss. You're starting to learn how to dance in the school. It's painful, and it takes time, and it might be not fun anymore. And those years are filled with effort, tears, setbacks, lost hope, varying levels of motivation, ups and downs, defeats and victories.
And then, maybe, if you're persistent and lucky, you might rediscover the joy from your childhood again. And that is the point where you know how to dance as professional, and you feel it and enjoy it as a kid. That is the integration point: your inner child integrated with an adult to form a mature creature.
For me, that is the metaphor of life. You go from childhood - which most people enjoy - to sometimes painful period of adulthood where you need to learn how to live and how to bring that joy back, and when you're done - you are a mature person. The one, who has a deep understanding of life and know how to enjoy it and appreciate it.
It is not about just rediscovering what was lost during adulthood. It's about bringing together all sides: mind and body and soul. It's this three-dimensionality that gives new depth to the joy. That is the whole point of growing up - to lose joy so you can find it again in a new broader sense and with new intensity.
Childhood is about not worrying about judgments from other people. You have no notion of shame, and you are yourself. You loose it in the process of growing up but rediscover later if you are lucky. Maybe that was the meaning of Adam and Eve story. Becoming aware of themselves and ashamed of whom they are expelled those two from the paradise. They lost themselves. But the way back is also possible as the story tells us.