For the posture adjustment during meditation at this stage is simply noticing if the sensation arrises that you need to physically shift your body or itch, just take a breath to give yourself a moment to notice that you physical need that adjustment of if your mind is just using it as a distraction to “get out of meditation”. Take this as intuitively as you want. Overall, especially if you’re meditation for over 10 mins, your body can start to develop some “bad” posture habits that can strain the neck, spine, etc. so it’s best to set yourself up at the beginning of your practice and then use best judgement if you need to shift. It will also start to get easy to get back into the meditative state fast the more we practice. - Carolina
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