Clearly distinguish full and empty; substantial and insubstantial; body and spirit. This happens naturally on standing or sitting: the body sinks with gravity and the spirit lifts with levity. And even more strongly as the standing body becomes single-weighted: the weighted side becomes full and the free side becomes empty. And on turning the waist: the body is thrown away centrifugally whereas the spirit (mind) gathers centripetally at the still centre.