"Flow" is the state we get into when we are challenged to sharpen our skills to accomplish a task. The athlete, the scientist, the gardener, the mechanic, the artist, the chess player all feel flow when they are working at their best. Flow is the optimal state of human experience, meaning it's the state most fulfilling to us.
Reading the book has really inspired me - of course as an artist I relate to the state of flow while I paint, but also for everyday, non-art experiences: I am finding so often when I want to disengage and tune out and watch tv or hang out on the internet or otherwise waste time, that it's equally restful and relaxing to actually engage. There is fulfillment in the everyday contemplation of what is in front of us.
I am reminded of a quote by Thomas Moore:
"Simple gestures taking place on the surface of life can be of central importance to the soul."
Painting and drawing could be called "simple gestures" - really, it's just pushing colored mud around with a hairy stick - but anyone who has tried it understands that it can take you pretty deep - through a quagmire of wrestling with our deepest fears, and occasionally through that to a place of peace. To where time and self-consciousness stop and we can just Be, without evaluating or worrying.
Maybe all we have to do to access the soul is to set up a space with a few objects on a table and some lighting, and look.