I use online chess tactics problems to assess how good my brain is that day. I estimate there's a 300+ ELO variance, perhaps even more, in my performance between when I'm tired and when I'm rested.
300 ELO points between 2 players means that the higher rates one wins about 9 out of 10 games against the lower rates one. A huge difference in performance.
First thing I do at my computer if I am groggy is to do chess tactics. Based on the results, I take a break or continue with my actual work. I should probably be looking at ELO as well, I just go by numbers at this time !
300 ELO points between 2 players means that the higher rates one wins about 9 out of 10 games against the lower rates one. A huge difference in performance.