On this blog I often say that planning is as important as writing. Not more important - but as important.
Above is another example of that, this time from JK Rowling. The image (click it to enlarge) speaks for itself really. Planning doesn't need to be neat, it doesn't need to be fixed in stone, it doesn't need to be something you share with others. It's job is to keep you on the right track and to free your mind from plotting when you are doing the detailed writing.