Inspiration comes unawares, from unaccountable sources that have nothing to do with planning or intelligence. Let it cool ever so slightly, and you are left, pen or brush in hand, with no inspiration at all. Gifted people need not, therefore, make a song and dance about being or supposing themselves superior. They simply happened to be born with that fortunate, subconscious equipment of theirs, and the mystery exists independently of intelligence or ambition.
It is a matter of artistic instinct. In his own thoughts and feelings and way of doing things an actor is worth nothing or he is worth something. If he is worth something then he will try to be worth something more as is only normal in anyone who wants to get on. I can think of no other way to explain artistic development.