Sleeping is the best therapy you can ever have. You get to relax just lying there and dreaming of whatever you want. Of course you don't have to pay a dime to get a good sleep. So, why would you wake up the following morning with a sore neck without exercising overnight? I mean, should that even happen? Maybe you went to bed with the sore neck after a tough day. Or maybe you did a lot of exercise the day before in the wrong way. But I don't want to bet on any of these. Have you ever considered the connection between neck pain and pillow?