It isn't just spending 10,000 hours (see next story), it's how you use those 10,000 hours. Most of those who excel had mentors for much of that time. But even without mentors there's still this: you have to be 100% self-critical and 100% no-BS about where you stand during those 10,000 (and beyond!).
You will fail for many of those 10,000 hours. Maybe not big failures, maybe only intermittent failures, but you will fail. I believe failure is good. Failure tells you something about what you don't know or see and gives you a place to start working. Now, some of that is my Silicon Valley upbringing. Failure is a rite of passage in Silicon Valley. Indeed, venture capitalists often tend to prefer those that have failed. As long as they're self aware about it.
When you fail you must do a number of things. First, you have to admit you failed. This is a bigger hurdle for most people than they think. The natural position is to just get defensive. When it becomes clear that that won't work, they'll try to point to a positive small bit in an otherwise big failure. Or worse still, point to someone or something else as contributing to the failure. No. You failed. Acknowledge it. Accept that your mentor, your co-workers, your advisers, your investors, your peers, your friends, your family, or whoever is telling you that it failed have a clear and reasonable view that you failed. Accept that even if you think something about what you did worked. If you can't accept the failure notification, you can't get to the next thing: analysis.
What exactly did you fail at? How big was the failure? What could you have tried differently? What paths did you reject in doing what you did that you need to go back and re-examine? Make sure you absolutely understand why others are judging what you did as a failure (if this is a self-judged failure, make sure that you're right!).
Finally: fix failures before moving on. If you keep failing at getting focus and acuity spot on, for example, it makes little sense to try to improve your post processing skills. You'll be fighting your previous and continuing focus failure in the pixels you're trying to nudge and improve. You don't build successes by trying to stack something on a failure.
So, if you spend 10,000 hours just doing the same things over and over and failing in the same ways, you won't become an expert. Find a mentor or peer to help keep you focused. Push yourself to fix things as you discover they're broken. Build on successes, not failures.