We are comprised of both material parts and immaterial parts. Your material parts (skin, organs, limbs) are the things that are affected by disease and stress. You immaterial parts consist of every thing that cannot be touched or handled physically (mind, thoughts, beliefs, desires, emotions, feelings, soul, will). When your immaterial parts are affected due to an emotional event or trauma then your physical body responds as it is programmed to do. Your heart rate may become elevated, your may perspire, your breathing might increase, and other physical reactions will take place. How you respond to the difficulties in every day life will affect your body.
With the pain of Fibromyalgia, the goal must be to glorify God in your life in spite of how painful your muscle pain is. The more you grow spiritually, and the more you apply biblical principles to the issues and problems in your life you may find relief from some of the pain associated with Fibromyalgia.
This is possible because as I said above your thoughts have a great impact on what happens in your body. When you are tense or fearful your body responds with physical tension (such as a tension headache). What then happens is a cascading effect as you sense the cycle beginning, and you then begin to fear the pain which creates more tension.
We are destroying speculations and every lofty thing raised up against the knowledge of God, and we are taking every thought captive to the obedience of Christ, 2 Corinthians 10:5 (NASB)
While I understand that the pain of Fibromyalgia does not originate in the thoughts, it can be exacerbated by the thought life. Taking every thought captive to obedience means learning to glorify God in your thoughts by replacing the fearful ones with faith and truth. It means to replace the self-pitying thoughts and beliefs with thoughts of thankfulness to God. Further, it means to begin to meditate on the sovereignty of God and what that means with respect to your suffering.
Understanding that a sovereign, loving God has allowed you to suffer with this pain might be a thought you will have to prayerfully adjust to. It is not easy to be thankful for pain, and it is not easy to accept that God has not only allowed it, but perhaps has brought it into your life.
""Shall we indeed accept good from God and not accept adversity?” Job 2:10b (NASB)
Just as it was with Job, God is in control of how much pain enters our lives. He has a purpose and plan for all of it with the ultimate goal being to conform us to the image and likeness of Christ. In this sense, the pain is a good thing because it is a part of God's plan for your transformation (Phil 3:10). This is why what you do in the pain and what you do with the pain is so very important. Thanking God for the pain is one critical piece you will need to come to grips with.
Then begin to think about how you can fulfill the responsibilities God has placed in your life. The things you are called to do daily are also no mistake, they are a part of God's sovereign plan for you. He has enabled you to do what He has called you to do each day. Sometimes it means fighting through the pain with thanksgiving. What can you do today to show love and serve others rather than focus on your pain?