I've given this a lot of thought, mostly to try and justify the rather unexceptional and mediocre character of my own life, and I have come to the following conclusion. All successful (whatever that means) people are favored, but not all favored people are successful. It's all covered by the mathematical jargon "necessary, but not sufficient, condition".

Exceptional people in any category are naturally talented, work very hard, and they are lucky. Luck does not necessarily mean the proverbial unexpected career break, like having the headliner get laryngitis so you can fill in at the last minute and steal the show. It also covers intangibles like not having been born in Constantinople while it was being sacked by the Turks, or not getting hit by a meteor during surgery.

As a sailor, this type of thought has always crossed my mind. The sea is unforgiving, it will usually crush the arrogant, the unprepared, the incompetent, the lazy, or the inexperienced. But sometimes, real idiots get away with incredibly foolhardy behavior, and other times master mariners go out and are are never heard from again. Life is not chess. It is backgammon. Earned skill and inborn talent are essential in the long run, but each play is ruled by the dice.

And of course, you can always argue that even the most personal and self-generated factor, the inherent willingness to work hard, may be determined by a gene you inherited from your parents, or a random experience you had as a child, or that you had a balanced diet growing up.