Do stretch exercises periodically while you are cutting/sewing. I hunch my shoulders up toward my ears, hold them for a few counts, then push them downward as far as I can go for a few counts. Turn your head side to side. Any excercises that will strengthen your core and ease the tension on your rotator cuff should help. (I usually call that a 'rotary cuff' and get laughed at!!)
I finally went to a chiropractor, got some good therapy and he taught me a bunch of exercises that really help. Gotta take care of our quilter bodies!!