The condition of the body follows the intention of the mind; the intention of the mind also follows the condition of the body.
The sleepy body (heaviness, slothfulness, energyless-ness) is a condition for dull or fantasy-driven or dream-like mental actions.
I see the posture drop. I see the mind become foggy and dreamy thinking (fluid and loose association) take over. I see sleep slowly and insidiously crawl in from an unseen bottom like a mist filling the space around a creek early in the morning… there was clear sight under the luminous darkness of the moon, but as the mist-filtered light emerges, the eyes are fooled into thinking all is light – it is at this moment that the fog is mistaken for the emptiness of “just sitting”; this is when the “self” becomes reified in a sleepy practice.