Programming ability is more like athletic ability than most people want to admit. Some guys just get better, faster. Some guys can't ever break certain plateaus, no matter how hard they try. In golf, it's probably possible for anyone to go from a duffer to a scratch golfer. But it might take 20 years of work for someone who isn't set up with the right natural gifts. Quality and amount of instruction and practice will determine some of the pace. But some people will just get it faster than others. And even "elite" golfers simply won't be as good as Tiger Woods, ever.
I used to be a good skateboarder. There were guys I skated with who could learn the tricks 5 times faster than I could. I don't know why. We all skated the same amount... in fact, some of the guys who were better than me skated a lot less than I did. They just had something clicking that I didn't have.
I'm a proponent of self-improvement. I think most average people can develop skills far and beyond what they give themselves credit for. I hate to be the guy who is arguing for mystical innate ability. However, it seems naive to claim that it doesn't exist.
To end this comment on a useful note, the one thing I noticed both with the good skateboarders and the good programmers I know, is that they would 'go big' when practicing. the skaters would try something hard and figure it out until they got it. They wouldn't just sit around and do the same kickflip in a parking lot over and over again.
Likewise, the good programmers I knew would always be seriously challenging themselves. For practice programs, they wouldn't just write a dumb fibonacci generator. They'd write a full blown throttling distributed network file copier, or a scheme compiler in postscript. Serious, hard projects for practice. Most programming is mundane and you can go for years without getting any better. The best guys I know are never complacent with doing the same boring shit all day - they'd always challenge themselves.