Some time ago I was arguing with Weegoddess about the 10,000 hours idea. This theory says that all that separates people who are experts from those who are just able is the practice they put in. I think that's wrong, and a dangerous idea to promote.
In the link above (which I admit is quite long but I promise is wholly worth your time) Scott Alexander at Slatestarcodex examines the question of what makes someone good - really good - at something, in the context of our society's insistence on tying self-worth to intellectual attainment. But it bears on the 10,000 hours idea as well because Alexander argues (and I believe) that it's not just a matter of practice or dedication or hard work.
As Alexander notes, you can't tell a depressed person just to "get over it" or "cheer up" and if they work really hard at it then they'll get better. It (depression) doesn't work that way as I keep reminding myself while I fight through this season. What it comes down to is a combination of factors, not least of which is that some people have innate talents. Some people are good at math; some are good at art. Some people are good at medicine and some people are good at raising healthy children. To say that what separates someone who's a math whiz from someone who never really did understand calculus is just their level of practice and dedication - 10,000 hours is all - is wrong and dangerous. It hurts people, and it hurts society.
If you can make it through Alexander's blog entry there's actually a follow-up that I'll link to if you want but really you should just add SSC to your blogroll because holy wow can that man write.