Relationships that are causing you nothing but headaches are to be allowed to die a natural death and replaced with a more useful one. Harsh but true! Sorry.
Anybody who has ever tried to write, work, or complete any project when they are extremely tired will have an idea of what I am talking about. Ability to focus will be nearly impossible, most of the words written won’t make sense. The mental function will be extremely slow. Yes, that is the life of people with fibromyalgia.
What else do you need? I think you should be focus, persevere, manage your time wisely, make some strict rules for yourself, and keep motivating yourself by tracking your progress. All these help me derive happiness at what I do.