I think that focus, tenacity, and perseverance are the three most human qualities most correlated with success. While I think that these are mostly innate qualities, I think they can be nurtured and significantly strengthened.
I got my electric guitar out of the attic for my older daughter who takes guitar classes at school. They do classical guitar the first half of the year and electric the second half.
My guitar has been calling to me. I don't mean that I've been having hallucinations, it's just that I feel a strong attraction to it.
When my younger daughter was 9, she and I were listening to "Johnny Winter And... Live" and we started talking about the music. She really dislikes his voice, especially when he hits the high notes using a sort of gargling falsetto scream. I told her I rather like that style of singing but could understand why she didn't like it.
I then went on to say the he was (is) a truly great guitarist. I wanted to then continue by turning that statement into a lecture about focus and tenacity so I pointed out that one of the reasons he's great is that he basically plays guitar or listens to music every waking second. I do believe that's one of life's most important lessons: success is more due to focus, tenacity, and perseverance than any other quality.
However, I was thwarted in delivering the rest of the lesson because the conversation went something like this:
Daughter: But you're a great guitarist and you don't play guitar all the time.
Me: No. I'm an okay guitar player, Johnny Winter is a great guitarist.
Daughter: Well, I think you're a great guitarist, daddy!
So she melted me then and there, rendering me incapable of continuing the lesson, even though my first thought was, "I'd better get her ears checked."
Unfortunately, the flip side of the focus, tenacity, and perseverance coin is obsession. Obsession is unhealthy in and of itself, but also seems to be closely related to drug addiction and alcohol dependence. That certainly was true for Johnny Winters and who knows how many other dead or ruined rock guitarists.
It's a fine balance between being obsessed enough to achieve success (how ever one wishes to define it) and staying healthy and reasonably balanced. I think it might be mostly genetic though.
 I feel that there are three levels of guitar virtuosity: guitar owner, guitar player, and guitarist. I'm somewhere in the guitar player range - on a good day.
 Great guitarists seem to have three qualities: (1) obsession, (2) huge hands, and (3) steel belted fingertips (mine blister quite easily).