I'm struggling lately with being tired all the time. Some of it is work stress and a personal issue, but after reading this article on SparkPeople, maybe it is at least partially from overtraining. I want to try taking a few days off, but it scares me to death that it will cause me to gain back some weight or I will totally lose motivation and quit working out all together. I have an upcoming annual physical, so I will definitely talk to my doctor about it to rule out any physiological problems.
In the meantime I think I should "play it by ear" and let my body be my guide. If I am truly tired, I will rest or do something short and light.
Edit: Let me add that I do already take rest days... always have. I rest at least one day each week and sometimes two. It just seems lately that might not be enough.