RSI? I can get through maybe a page of handwritten text before my hand hurts too much to think, while I basically always run out of things to say before typing enough to need a physical break.
It sounds like you probably have too tight a grip and write more from than the wrist and fingers than the shoulder and forearm. This was a solved problem more than a hundred years ago, when it had to be; in the U.S. it's famously associated with the Palmer Method[0], although Palmer didn't originate it by a long shot.
(While these books, of course, are written for use with dip pens, and frequently taken up by users of fountain pens today, the methods described do work with ballpoints, rollerballs, gel pens, pencils of not too hard a lead, nearly whatever you have lying about.)
Of course, retooling is almost certainly not worth it for you, unless you're dying for a break from computer screens (the only reason I ever write by hand anymore). But I'll leave the link in case anyone is curious, either for their own work or just to know what people used to do with a pen, and why writer's cramp was not as serious a problem before typewriters and computers as we might suppose it was, by how frequently we tend to induce cramp on ourselves.
It's true, I have no reason to learn a different method as I have no reason to write anything by hand, but thank you for sharing the information. I suppose I had just assumed it was something people got used to, or that regular practice would build up hand strength in such a way that it would no longer hurt.
