In the book, The War of Art, author Steven Pressfield talked about what separates amateurs from professionals and how a professional became who they are.
I will write about what these aspects mean to me personally.
The professional reinvents herself
The pro knows nothing, no matter how good, stays the same forever, himself included. He learns and transforms as the work calls for the changes on his part. The pro has many solid examples to learn from the recipients of the Kennedy Center Honors.
The professional is recognized by other professionals
The pro recognizes another pro and her craft. The pro can tell who is the diligent apprentice, the pretending wanna-be, or the real deal.