Tom Doak beat me to posting my next point which I thought of just after my last post, but have been too busy to post.
As a computer science professor, I had lots of students tell me that my lectures were perfectly clear and that they understood them fully. It was just then when they went to put them into practice, they could not accomplish what they wanted to do. PRACTICE is a major key. After they struggle and internalize what they have learned, they become somewhat adept. Some accomplish it with very little practice and become very adept. Others practice a lot and only become somewhat adept.