I can relate to this so much. Writing not selling (or, for that matter, tap dancing) is where my skills lie but ... as a freelancer, the lines are still blurred a bit...and not just because I write both ad copy and magazine articles but because I still have to pitch (and sell) an editor on a story idea and still have to pitch my books to publishers and agents (and when they come out, market them and myself to an audience). Being able to pitch via email is a big advantage when you're introvert because then you can send it off and let it go, come what may. Of course, it's not always possible to do so. Anyway, just wanted to say, as a fellow introvert, I feel you on this.