Stretch often and get a good cervical pillow. Frigging life changing on aches and pains when your body isn't near its limit simply keeping your head turned or letting a leg flop over. The practice also makes it easier to identify when you're reaching your limits doing normal stuff, too, so dumb little injuries from pulling something happens far less often.
Cervical pillow works great when I sleep on my back which I kind of hate. And if I sleep on my side I still get a sore neck the next day even with the cervical pillow.
I guess I need to find a thicker cervical pillow with just the right height but it's not easy...
I don't think you'd want a cervical pillow for sleeping on your side would you? A taller memory foam pillow with support would probably be better on your side to keep your neck straight.
Yea, a plain cervical pillow won't help with side-sleeping, but they do make some weird ones that have way fatter edges and a sunk muddle, or even all the way to a weird boxy starfish shape. They're all designed to enable comfy back and side sleeping, since you can move about the pillow depending on what you need.
They seem awkward, but they're fine, even in a normal pillow case.