In college, I wanted to be a professional science fiction writer. I wrote two novels, then got sidelined in fanfic, and for a while I felt guilty that I wasn't getting anything done on my original fiction, and felt like I had to justify my fanfic writing to my non-fannish friends. Then I realized that I didn't really care about the being published part--I just wanted to write. Being published is hard work, and supporting yourself with writing is even harder, and I realized it wasn't worth it to me. I'd rather write good quality fanfic, and have my stuff read as I write it, than struggle for years to make it professionally. It is no less fulfilling for me, and a heck of a lot less stressful. And I am called to do something else with my life--writing is my primary hobby, it's not my life.

YMMV, of course, but it might be interesting to ask yourself if you want to be a professional writer because it's what you really want or because of general social pressure that says writing is somehow less acceptable if you're not making money off it.

The nice thing about NaNo is that it doesn't matter if everything comes together as you write it, because that is what NaNoEdMo is for. NaNo's a great tool for people whose editing brains get in the way of their writing brains. (This is my problem with writing, if I can't get the phrasing I want I stop rather than just getting something on the screen and polishing it up later.