Artists, writers and people in creative fields are entrepreneurs by necessity. Nobody gives them a paycheck or picks up their medical insurance. The ones who succeed learn to think and act like 'independent operators.' I think people who are technically 'employees' have to think this way as well. The company is not looking out for you.
Turning pro is a mindset. If we are struggling with fear, self-sabotage, procrastination, self-doubt, etc., the problem is, we're thinking like amateurs. Amateurs don't show up. Amateurs crap out. Amateurs let adversity defeat them. The pro thinks differently. He shows up, he does his work, he keeps on truckin', no matter what.