karenm36

That same thing happened to me on my first quilt. Someone recommended using "Machingers". These are quilting gloves that have a bit of "tack" to them so that it's easier to have control of all the fabric without using so much of your muscle strength to do so. And I was so pleasantly surprised...they made a BIG difference! You can get them at most LQSs.

JulieR

I often find my shoulders up around my ears when I'm quilting, so I've made a new habit: every time I lift the presser foot I make a point to drop my shoulders. Helps keep me from tensing up so much. :)

amma

Set a timer for 15-20 minutes, then stop sewing, stretch, raise or lower your chair an inch or two and then reset your timer.
Moving your chair up or down just that little bit will make a big difference :D:D:D

QuiltE

Ditto on get yourself up higher on your chair.
For all my sewing I use a drafting chair ... the regular office chairs are just a little too low for me even at the highest point. The drafting chair's lowest is the same as the highest of the office.

And in so doing, you may discover it too far to the ground .... and may need to put a platform for the footpedal and your feet.

As said .... relaxxxxxxx (yes, easier said than done!)
and breeeeeeeeeathe deeeeeeeeep, innnnnnn, ouuuuuuut!!!! :)