Back when I was a teenager, I read Kurt Vonnegut's Breakfast of Champions. I hardly remember anything about it now, not even the central plotline; but one bit has always stuck with me. There's a character in the book who's writing his own book and has everything planned out ahead of time. Then suddenly one of his characters surprises him, doing something he didn't anticipate (Hmm, or maybe one of Vonnegut's characters surprised him; like I said, I don't remember much about it anymore).
The reason this scene stuck with me is because it rang so true to my own experience. When I'm in the zone, my characters actually do write themselves. Sometimes they even dictate to me. For instance, the MCer in the story I'm working on now is wittier than I'll ever be, but his dialogue came naturally to me (Yes, it's a "him" this time - but the story's not yellow. I wouldn't dare!).
I also wrote most of the rough draft without fully understanding the MCer's methods. That's where the title of this post comes in. I go mostly on instinct, trusting my subconscious to make sense of things I don't consciously understand. Now, my MC'er in this story is pretty capricious, so I assumed he was going on instinct, too...until I slipped in a particular Easter egg. The MCer's subject is making a wild guess about his plans, but after I wrote the guess, I realized it was right! I'm still not sure if the MCer realizes what he's he's doing, though. He hasn't told me.
Anyway, more on all this when I publish the story and post my "Peek Beneath the Duct Tape." For now, I just want to marvel at the things my brain does when I'm not looking.