The old saying is partially metaphorical, but then partially literal sometimes too. You write, or engage in whatever other creative act in a fit of inspiration, rapidly belting off various ideas, sometimes only dimly connected. The task after that is to take the raw output and shape and edit it, taking care to add connections to those ideas you've thrown so sloppily about, or trim and edit here and there. Keep in mind the reader, or the listener, or the observer, and think about what they are thinking when they look upon what you are trying to communicate.
You could say the creative act is almost entirely subjective and instinctual. You are merely trying to externalize what is inside of you, regardless of what it means, or whether it is correct or useful. The editing is a social act. It is the attempt to shape an act of communication and establish the connection to another intelligence. The objective takes shape after others witness the externalized subjective, and then incorporate it into their own subjective experience. The objective is the subjective amplified and averaged in various ways.
The creative act is usually pretty fun. The editing is usually drudgery. But it doesn't have to be. It is all necessary.
