When I first began to paint landscapes many years ago, one of the most helpful ideas I came across was the description of the sky as a vault, arching up over us as well as out into the distance ahead. As a child, I often lay on my back in the grass watching clouds or stars at night. But, somehow, as adults we lose that sense of wonder at the thin little envelope of air and light that surrounds and protects us. About the same time I read that description, I started laying down on the grass in our garden and looking up again. Very edifying. I highly recommend it.