Here is a perfect practice in un-thinking. Draw a continuous, tangly scribble as big as your paper with a pen or pencil, then color in the shapes you created with crayons. It may look random, or you may notice patterns emerging. Either way, the smooth, flowy action of creating loops and coloring helps to calm the mind.
When I was younger, my siblings and I would collaborate with scribble drawings. One would make the scribble, and the other would color it in. This is fun when you have a long wait with someone and you need something to pass the time.