The overall fitness is going to definitely have a positive effect on the perceived energy levels (my Vo2 max is at its highest ever). On the other hand, I have been very fit at other times in my life but have never experienced this "my head can just go on" feeling before. I used to take conscious breaks, do NSDR between meetings and other energy-replenishing tricks because I __needed__ them. It feels like now I don't

You mentioned that you took up CrossFit after starting creatine. Did your previous fit phases include lifting heavy weights?