A similar thought from Heinlein:

To me, the acme of prose style is exemplified by that simple, graceful clause: "Pay to the order of. . . ."

Source.

I have heard both my father and my brother, professional musicians, mention the tremendous difference between professionals and amateurs. There is their differing levels of skill, of course, but the more fundamental difference is the seriousness that a professional brings to the work. There's nothing like having to put food on the table and a roof over your head, to give yourself that seriousness and get the work done, no matter what.