“You have all these people trying to come up with formulas to beat the market. The market is not a science. The science may help increase the probabilities, but to excel you need to master the art of trading.”  
– Mark Minervini, Stock Market Wizards
“After a certain high level of technical skill is achieved, science and art tend to coalesce in aesthetics, plasticity, and form. The greatest scientists are artists as well.”

To achieve trading greatness, one must first become an artist. To become a true artist, one must first master the art.
What does it mean to “master the art” of trading? What kind of nuances and subtleties are involved?  What range of experiences, processes, and deep situational knowledge is required?