While I was doing a set of pieces for a show about cats and dogs, I set myself a design problem making a loose, free drawing of a cat.
I wanted to draw it as a child would draw--just go for it!
The other restraint was to lift my brush as little as possible, making the expression in one continued line. To be as free as a child in making the image.
The head outline was one line. The body another. Face and claws were last.
You almost have to do this holding your breath.
It's harder than it looks.
It's also a good discipline for visualizing what you are going to do before you do it.