Here's what I do. I just sit or, more often, lie still and just notice where I'm holding up my body a little more tightly in places that are achey than in those places that are not. It's usually my lower back, shoulders, just under my shoulder blades and my neck. After I take note of where the tension is I consciously make those parts release the tension and relax. When I am doing this it is so easy to see that my body has learned to hold those places tighter as if it thinks the extra tension is needed to hold up the rest of my body. I know that when I release these places and relax, that my body doesn't just fall over from the lack of tension that it has memorized while I wasn't paying attention. It thinks that I need that added tightness to stay upright or to keep from falling through the bed. People say what I'm describing is the body holding onto stress and I'm sure that this is probably the origin of it but I also know a lot of mine is body memory. If it were only stress then I wouldn't have tension all the time. I'm rarely stressed but always have tension. I think if I continue to practice this, over time, I can teach my body some new memories, like that it's okay to let go. I hope that feeding it new memories that it will eventually learn to release into a permanent relaxed way.
Maybe tonight while you are in your bed getting ready to fall asleep you could scan your own body for tension, then release it and let the bed completely have you. You will be amazed and your body will sigh in relief.
note: It's not funny but it does seem odd that between finishing this post and the time it is scheduled to post, B sent me a text that his back went out. Crazy timing.