Athletes can push themselves very hard, but a good athlete also knows when she's pushed perhaps harder than she can take. She doesn't beat herself up for being sore the day after a grueling bit of exertion. Nor does she castigate herself for not being an olympic-class swimmer the first time out if she's spent the last ten years training as a pole-vaulter.
My brain is battered. In an ideal world, I could give myself recovery time, but deadlines suggest that there's going to be a bit more pushing before that happens, and I'm going to pay for it. I'm throwing new challenges at my little brain, and it may not be up to them all just yet.
BUT... I in no way need to blame myself for feeling worn-out. It is a natural consequence of over-exertion, and initial clumsiness is to be expected when exercising new mental muscles. I will likely stumble a bit in my upcoming presentation, but in the long run, it's going to be o-fc*king-kay.