Writing is a business. I fail because I sometimes lose track of that notion. I get wildly carried away with some screwball idea, only to realize later that my project's marketability factor is ziltch. (I mean, come on. Modern day elves? A whole trilogy of modern day elves? where did I come up with that gem, anyway?)
So, now a days, I try to keep my eye on the prize before I even sit down to write. I ask myself, where am I going to market this? What are my secondary markets? What is my word length? What is my intended audience, and what are the rules? Can they have sex, not have sex? Am I supposed to focus only on the primary MC's or does the pub appreciate a good sub-plot? Stuff like that.
I've had a few nibbles of interest with my newer, more focused stuff, so I guess it helps.
But, deep in my heart, I still want to write about modern day elves. *sigh*