I was reading one of my favourite blogs, The Longstockings, and came across this piece of writing advice from Lisa Greenwald: "think, think, think about your book!" Her point is that the work of writing doesn't occur just during the time that a writer is sitting at the keyboard or in front of a blank page. Rather, much of the work of writing takes place in the writer's mind during the in-between times -- commuting, walking, showering, gardening.
Perhaps this bit of wisdom about writing tends to be placed in the background in many books on writing just because of the truism that until the words are on the page, the story hasn't been written. Many a wonderful idea for a story never makes it to the page. For many writers, the anxiety about putting words down prevents them from even starting. So there is a lot of advice focused on coaching writers to sit down and write -- to just get the words down, and defer any editing and much thinking until a second revision stage.
But, in fact, the daydreaming and thinking time periods are also essential. The story doesn't spring to life only at the keyboard. The story is churning away, under the surface, whenever we let our minds have the freedom to do so. For me, it is so important to have times in my day that are not filled with other fully engaging cognitive tasks. When I use up my thinking on work tasks, or reading, or social interaction, or any activity that is filled with words, my mind does not have the unstructured space it needs to drift to the story at hand. If I let it have the time, my unfettered mind does a lot of the writing for me, in between each session at the keyboard.