Happy to have you here, debbieko, or anyone else who can relate to what I am writing. I actually wasn't thinking about meditation there, but more about doing stuff, like eating, mindfully. But yes, it happens to me during meditation also.
Over to posture.
I have been slowly training to sit without support for my back. Not so much because some gurus tell me that's how to do it, but because if I am going to sit mindfully for several hours a week, I want that sitting to help me gain a good general posture and musculature, not exercise my slouching.
When I started my practice, it was painfully clear that I couldn't sit still for half an hour without leaning against something. So I have been practicing free sitting for shorter times (10-15 minutes) and I've had a lot of help from a couple of good (i believe) guides on the web. What I especially learned from these was the importance of the slant of the pelvis, for getting a good angle in the back.
http://www.freebuddhistaudio.com/texts/ ... _Guide.pdf and
https://www.youtube.com/watch?v=9FA599jvADE Today, I was able to sit a full half hour in a free half lotus position, with only very minor pain in my back (although, my leg went horribly to sleep, but that's another story). I still struggle both with being relaxed while also unsupported and upright and with being mindful about pain, but I am hopeful that I will learn also these, with time.
I know how to tell an arm to go limp, but how do you relax those deep abdominal muscles, that aren't under direct control by the conscious mind?
Stands at the sea, wonders at wondering: I a universe of atoms, an atom in the universe.
-Richard Feynman-