If you have CFS and/or FM, too little activity leads to deconditioning, while overdoing leads to increased pain and relapse. Learn to manage energy as you do money. The tendency to overdo usually outweighs the tendency to underdo, requiring that we prioritize. How do I choose to spend my energy? How can I attend to my responsibilities to others while taking care of my own health needs, rather than focusing on one at the expense of the other?
Identify counterproductive behavioral patterns and learn to schedule rest and relaxation intervals, whether or not you feel fatigued. Complete tasks in small steps interspersed with rest periods rather than one big chunk. Be aware of early signs of fatigue or increased pain, and stop.
(Source: Chronic Fatigue Syndrome, Fibromyalgia and Other Invisible Illnesses, by Katrina Berne, Ph.D.)