I wrote my first novel when I was 10, my second when I was 11, my third when I was 12... well, you get the idea. I understood that a concept called "editing" existed, but it seemed like a daunting thing to start. At that age, I just enjoyed the process of storytelling and creating characters, and so for many years I'd write one draft, then move on to a new story, and then repeat the process. I'm 27 now and I have a LOT of first drafts scattered about. Some are still in my parents' house.
With the novel I wrote in 2005, I started doing some minor editing -- tweaking, really. I was scared to scrap whole scenes and rewrite them. Before I got over that fear, I realized the concept wouldn't be saleable as a first novel, and I had another idea, one that had been gnawing at me for some time, that I wanted to work on much more.
So I began my current novel. I wrote the first draft really quickly, recognizing that it was little more than a way to get my ideas down on paper in a mildly organized fashion. After I finished that draft, I tried to "edit" within the same Word file, but I realized I was just spinning my wheels, taking out unnecessary words but not working on the plot or rewriting scenes that were awkward. I started over in a new file -- draft 2.
I'm putting this novel together in layers: draft 1 was a skeleton of the plot; draft 2 is a more organized version of the plot, with better hints of the ending in the beginning and better use of certain plot threads from one chapter to another; draft 3 will, I think, be mostly about voice and word use. I'm not sure yet if there will be a draft 4, but I won't be afraid to rewrite this thing again if it comes to that.