There just happen to be people like that. They’re

In his novel Norwegian Wood Haruki Murakami writes: 

There just happen to be people like that. They’re blessed with this  marvelous talent, but they can’t make the effort to systematize it. They  end up squandering it in little bits and pieces. I’ve seen my share of  people like that. At first you think they’re amazing. Like, they can  sight-read some terrifically difficult piece and do a damn good job  playing it all the way through. You see them do it, and you’re  overwhelmed. You think, ‘I could never do that in a million years.’ But  that’s as far as they go. They can’t take it any further. And why not?  Because they won’t put in the effort. Because they haven’t had the  discipline pounded into them. They’ve been spoiled. They have  just enough talent so they’ve been able to play things well without any  effort and they’ve had people telling them how great they are from the  time they’re little, so hard work looks stupid to them.