I just finished reading blog post Paying Yourself to Write by Tami Moore where she in turn references blog post Paid Writer by Bria Quinlan. Bria suggests setting up a pay scale (e.g., $10/hr for writing, $5/hr for research, etc.) and keeping track of what you earn. The idea is that putting a dollar value on an effort that (more often than not) results in no income helps keep you in the mindset that writing is still serious business.
I think Tami takes this concept further by saying, in so many words, it's not about the money but about how you treat this gig. Whether you're published or not, paid or not, professional or not: are you acting like you're like a published, paid, professional?
While both Bria and Tami embrace the idea of the pay scale, I feel Tami strikes closer to the heart of the matter: it's less about the money and more about your behavior. In short, are you treating your writing like an actual job?