As I discussed in my recent blog post on exercise, staying conditioned as much as possible is important and helpful in fibromyalgia, as it is in most chronic illnesses. What is not helpful are fools who use the research showing this to try to treat fibromyalgia as if it is purely a psychological disorder. Sadly, there are those who attempt to use the PACE study (a 2011 study that used cognitive behavioral therapy as part of a CFS treatment trial) in this way.
Below is an interesting article that discusses the problems with the PACE study. I would note that I consider Dr. Peter White, one of the researchers involved in the study, to be both an excellent researcher and human being. Looking at his direct writings, I do not see him saying that fibromyalgia is not a real illness. Instead, he speaks about the importance of treating the mind-body connection in all illnesses—which I agree is an important part of treating anything from cancer to chronic pain.