When my son (soon to be 21) was a baby, at that noble age when they sit beautifully straight, before the strain of walking has corrupted their posture, he used to sit and play with his toys, bolt upright and totally engrossed. Yet every time an aeroplane would fly by, without lifting his head, he would point up to the sky to acknowledge its passage. This was energetic attention – his focus on the toy also caused his awareness to expand and embrace his whole environment. And this ability – to focus on what's before and at the same time to expand the back to envelop the world – came from the beautiful poise of the head atop his perfectly straight and vertical spine. If you allow the head to crane forward in an attempt to give greater attention to what's in front, then you lose the bigger picture and you lose energy; central equilibrium – the absolute requirement of any energetic system – has gone.