Amateurs vs. Professionals

Seth Godin in Professionals are consistent:

Authenticity is for friendships.

Professionals simply show up. Especially when they don’t feel like it.

There are many corollaries to "professionals simply show up." For example, amateurs put a lot of weight on character compatibility with their peers as a requisite for doing the work. Professionals know how to establish good work relationships despite character differences.

Another corollary, this time by Steven Pressfield in Turning Pro: The amateur lives by the opinions of the others.