I try to draw every day, although what I call "drawing" most people might refer to as doodling, or worse...the deranged scribblings of a madman. Whatever. The point is to be touching pen or pencil to paper as much as possible, and whenever possible. I see it as my mission to wear out pens and grind pencils down to nothing. Why?
In every artform there must be some form of unstructured, non-goal-oriented improvisation time, in which the artist is free to explore and come up with new ideas. Otherwise, in my opinion, their work will stagnate. At least, this is what applies for me. Some of my most interesting concepts or ideas have emerged from my drawings and doodlings.
Also, quite simply, drawing takes up less space and material than painting, and its easier to come up with a new idea or theme on paper (a rough sketch, if you will) and refine it and refine it, until the point when it becomes time to take it onto the canvas.