There's an old story that's been told in various incarnations and media. Generally, it involves a young, hard working employee at some company who passes by the desk/office of a more senior employee. For the sake of this post, we'll call the young employee Bob and the more senior employee Joe. Bob passes by Joe's office almost daily and notices that, each time, Joe is just sitting with his feet propped up on his desk. It looks like Joe is staring out into space or even half-asleep. Bob, meanwhile, puts in long hours and keeps his nose to the grindstone. After a few weeks of watching Joe's apparent tireless slacking, Bob finally works up the courage to ask another employee why Joe hasn't been fired yet. Bob's fellow worker then tells him that some time ago, Joe was sitting at his desk, with his feet propped up, and came up with an idea that saved the company millions of dollars. I've likely butchered the story, though I think you get the point.
Daydreaming is the writer's best friend, just as in the example above. It's an opportunity to let the creative side of your brain take over and just wander. This leads to all sorts of ideas that you may not have considered while you were diligently tapping away at the keyboard to meet your daily/weekly word count goal. This is because when we are in the trenches of actively writing we are either trying to capture that moment of inspiration and emotion, or trying to slog through a chapter that's become tedious for whatever reason. Neither gives the writer much of an opportunity to sit back in the audience and watch what's playing on the screen. That's what daydreaming becomes in the context of writing a book: it's like hitting the replay button for your favorite movie scene to make you didn't miss something. It leads to far more introspection that you might even find during the normal editing process.
The kind of replay editing that I'm referring to is not so much to catch grammar and punctuation mistakes, as it's a sort of quality control device. Ultimately, the writer has to ask herself/himself: does this scene play out on paper/ebook the same way that it does in my head? If it doesn't, then it may be time to hit the replay button and fix what doesn't work. Alternatively, if what you've written mirrors what's in your head, then you know that it's time to move on to the next scene.
Another important aspect of daydreaming and its importance to writing - aside from the usual enjoyment of staring off into space - is the inspirational aspect. Sometimes we dwell so much and for so long on a story that we lose sight of what ignited the creative spark in the first place. Under those circumstances, daydreaming about your story can help rekindle that fire. As I mentioned in a previous post that I tend to listen to music when I write. I also play certain songs when I'm daydreaming and trying to work out a particular section before trying to write it down.
What do you see when you write or read?