You can never be great without practice. You can be very, very good with practice. But you cannot be great without talent.
That David & Goliath book talks about how MG kids who hot house themselves into a top school have a nervous breakdown in the first year because they find themselves with the uber smart and everything is going so fast, other kids get it fast and they are out of their league. I know one such kid. Got into Princeton and by January had to take year off, wasn't going to class. Back at Princeton after a year but with an easier course load.
