As it turns out, there is actually a name for the type of writing style that I have been embracing. Its call being a "Panster," because you dive in with no plan and essentially fly by the seat of your pants. It's quite fun, and I recommend you try it.
I've been enjoying my pants-seat flight, but occasionally I have come up against large character or plot problems that I would probably have avoided had I referenced a map before starting my flight. Then again, even when I did have a tentative plan, things kept changing and surprising me. Most recently, I had a character show up not at all where I expected him to, and that threw the plot for a bit of a loop, but I think its a better loop than it would have been otherwise. Even though it led to several days of beating my head against the wall debating taking up stamp collecting as my new hobby.
I worked through my stuck-ness by way of sort of mapping, sort of outlining, and generally writing things down in my absolutely abysmal handwriting. It worked, eventually, because I finally squeezed out a couple more chapters and got my momentum back. Now I'm just trying to sit really still so I don't scare it away.
Whilst I was plotting and mapping and generally driving myself crazy, I even made a couple of notes about the next thing. I'm excited about the next thing, and keep having to remind myself that I am determined to finish the first thing before I conquer the next thing. More on that later.