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I didn't win, but I decided to list my entry anyway:
I have been writing for a long time, but have not been able to motivate myself to focus enough on pursuing a career in writing. I guess that makes me a dabbler, huh? So my biggest challenge to a writing career is myself. I fear that my lack of focus on that One Thing I Am An Expert On, will hurt me in the long run. What if I chose the wrong thing? What if I should focus on Subject X when Subject Y is what is most needed in the market? So I remain a Jane-of-Many-Subjects-But-Expert-On-None.