In Malcolm Gladwell's Outliers: The Story of Success, he writes that the number of hours of practice that it takes to become expert in something is 10,000 hours.
I was happy to hear this because I can call myself an expert crochet artisan now. :) After years (and years and years) of 'practice' - making things, ripping them out, re-doing it, ripping it out, etc., I know that I have that 10,000 hours. Now, this doesn't mean that the ultimate goal has been met. In order to continue at a high level of whatever you do, you have to continue practicing.
There are so many pieces of knowledge and insight that Gladwell has written about that are truly out-of-the-box thinking - in this and his other books - that all I can say is - read the books!