Also, taking fatigue in another direction, I do pilates daily for back health (I've broken my back twice). It used to be I couldn't stand up for more than 20-30 seconds without major pain, but now my back is healthier than when I was in my 20s. Strengthening those core muscles will perform wonders -- I promise. A Canadian paratrooper with back trauma introduced me to pilates. He went from being bedridden/disabled to active again in 6 months.
Don't forget about the body in fighting fatigue. There's my plug for better back health.