Matt McCall over at VC Confidential, offers this excellent post on "The Passion For Greatness."
"There has been a lot written and speculated about what is the source of greatness. The two groups fall into the innate greatness camp and the passionate focus camp. Study after study has failed to deliver many points for the “innate greatness” side, but a growing body of research supports the grueling, demanding practice position.
While innate ability is obviously a key factor in grouping competitors (e.g. a five foot person is not likely going to make it far in basketball), the difference between good and great is "Deliberate practice".
Read Matt's entire article here.