Even the lucky and talented have to be taught the skills of their craft and continue to practice regularly. They just get to see a payoff earlier than everyone else.
Jascha Heifetz: "If I don't practice one day, I know it; two days, the critics know it; three days, the public knows it."
What is meant here by "magic?" To me, it seems that it is synonymous with effortlessness; anyone skilled in a craft makes it look easy. In order to create this magic, a person toils in private. Since no one saw the preparation, the result looks like it came from nowhere--i.e., magic.