Sometimes I'm feeling great and creative with a whole concept in mind, characters or a story.  But there are also times where I'm lost or stressed and not feeling great and the desire to draw is still there.  So I just start drawing lines.  Curvy ones, pointy ones, unpredictable movement and just try to free flow with it.  Releasing a great amount of stress.  In the process it ends up being a beautiful piece of art, after adding color and smoothing out all the lines and finding the hidden things I created.  This is beautiful chaos.