Pink put it best when he described Mastery, "As wonderful as flow is, the path to mastery-becoming ever better at something you care about-is not lined with daisies and spanned by a rainbow. If it were, more of us would make the trip. Mastery hurts." (pg. 124)
This is easily quite identifiable by many painters, musicians, architects, and the list goes on. To master something is to be familiar with every aspect of your job or skill. Even this is difficult to do and Pink also wrote it best when he said it takes at least a decade to actually master something if one was arduous at it. In other such cases it may take longer An example of such can be shown when Lars Ulrich, the drummer of Metallica, admits to having not mastered his skill in an interview by saying, "I suck," in a magazine. Keep in mind that he has been playing with Metallica for more than several decades and playing drums even longer. This shows how much hard is to actually master a skill. Even then, it is difficult to say if one has mastered a skill because there is still so much to learn about that skill. Just like the old saying goes, "The more you know, the less you know."
(In my project, it is best to keep my students from believing they are going to master their instrument within the year. If they gain this type of thinking, they may believe they may take it easy and never actually try. With this said, it is best to keep them from thinking they are going to be top-notched, A grade, or five star drummers.)