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 does not hesitate to ask for help
The pro believes in continuous learning, from anyone who can help to level up his game. Everyone wants the pro to be the know-it-all, and some amateurs pretend to be that all-knowing being. The pro, however, knows better and thinks of himself as a perpetual student.
The professional does not identify with his or her instrument
The pro does not get caught up on or identify with the instrument he uses to deliver his work, even when that instrument is himself. The pro cares deeply about doing work and delivering, not so much with what he needs to use.
The professional does not take failure or success personally
The pro is not emotionally attached to the outcome of his work. He does that, so the fear of rejection or other negative emotions cannot be used by the Resistance against us. The pro is invested in his work, and he self-validates objectively. The pro seeks to learn and grow by keeping an open mind about criticism, but he does not allow the Resistance to use the criticism against him.