Try not to think to much in the first rounds of work, try not to categorize it right away--because it's possible to shut something wonderful away by closing any avenue of choice. Just think of it as EXPRESSION. And let it be whatever it tends to over time. I've had four separate "short stories" end up being novels, because that was where they led. If you think of it as expression, it's a little less daunting, at least for me.