Last week (or so), at the class at Laurel Hill, I was reminded of the value of stretching while making a Zentangle. We'd made our first tile, and I had everyone stand up and do the "breathe and stretch" thing. The sighs around the room were my reminder.
I also find that I can sometimes develop a "death grip" on my pen. I relax, but my fingers often continue feeling cramped.
So, I've dipped into my yarn stash and made a cranium ball. I've recently learned that these are actually hyperbolic planes, but my language brain has always been stronger than my math/engineering brain so I will continue to call them cranium balls. They are just the right size for squishing and scrunching fingers into. I'm going to make a batch and let people use them during class.