It is extremely common, and something I think all of us experience at some point. As Anthony said you can check out my article Outrunning Fatigue and it should help to put things in perspective. Just keep in mind no one can do more than they can do, and some days you just won't be able to. Be fine with it, I know, easier said than done, but for now, temporarily, give yourself a break. You're gonna earn it, I promise, if you haven't already. Keep on keepin' on, DPM