Adding shadows to a drawing

We all learn to draw as a child via outlines – stick man, tree, sun etc. Of course some of us never grow out of that phase. At a certain stage, some notices a lot more details and then eventually there are those that add shadows to their drawings making objects look 3D.

Here is a video of how shadows changes a drawing.

Here is an interesting way to paint:

Exercise
How is this related to martial arts? What are you noticing more that you didn’t see initially?