Has this ever happened to you? You’ve had a niggling pain which has been bothering you all day and will not shift. Perhaps this pain is always with you, the result of a chronic problem.  A busy day has meant you had to push it to the back of your mind, but every time you stopped you were aware of it again. You longed to get home, get warm and get into bed. “A good night’s sleep will sort this out,” you said to yourself as you got ready to curl up. You shut your eyes and . . . that niggling pain seems to grow. You can almost see it, expanding like a great fat spider and taking over your body. The longer you…