I think I can describe setting up mindfulness of proprioception a little better.
Checking in with pitch, yaw, and roll wherever I feel my awareness to be can be useful, provided at the same time I am open to the possible movement of awareness (movement that can take place without any physical movement).
I find that a sense of movement forward and back, side to side, and around to the left and right is always present with my sense of location, and a little effort to distinguish the directions of movement from one another goes a long way toward the bottom dropping out of the bucket; the bottom can completely drop out of the bucket when the freedom of awareness to move is realized at the same time. There’s a sense of free-fall, that continues through the interplay of location and freedom of location with gravity.
Oddly enough, the net result is falling upright into one’s own skin:
When you arrive at last at towering up like a wall miles high, you will finally know that there aren’t so many things.
(Yuanwu, “Zen Letters”, translated by Thomas Cleary, pg 83)
The sense of location and the freedom of the sense of location to move are really a part of the movement of breath; if they are constricted, the breath is cut off. That is why Bodhidharma said, “have no coughing or sighing in the mind– with your mind like a wall you can enter the way” (Denkoroku, translated by Thomas Cleary, 3 pg 111). Through his use of the words “coughing” and “sighing”, Bodhidharma points to the intimate relationship between self-awareness, or mind, and continuity in the movement of breath; his direction only really makes sense when the exercise of equalibrioception and proprioception, the senses most identified with the physical awareness of self, is experienced as inherent in the movement of breath, as necessary to the continuity of breath.
Setting up a mindfulness of proprioception, or the freedom of awareness to move, in connection with equalibrioception, or the sense of balanced movement wherever my awareness is now, helps me to relax into my own experience, even if the only result is that I fall asleep.