Various spiritual practices instructions I\’ve tried to follow over the years on first encountering them are or at least sound descriptive, \”sit with your spinal vertical, as if you were being pulled upward by the hair on your head.\” My experience is that this partially true, but more powerfully, are descriptive. When I\’m sitting or even walking to the grocery store mindfully, my spine straightens, my posture is correct and it is going well. When my mind wanders, I slump.
Famously, Zen monasteries have a senior monk with a big stick to whack you when you slump. Done properly, this is compassionate feedback so you can correct a possibly unnoticed decline in the quality of your practice.