Usually I am pretty stubborn when it comes to resting at practice. Don't want to show weakness or some such crap.
Last night while fighting I noted that leg shots I had no problem landing at the start had become more difficult to get acknowledged.
I could still get them in hard enough, but when I did, it required extra concious effort to do so.
As I got tired my body attempted to conserve energy by cheating the shot.
I am not at practice to prove anything, I am there to learn and get better. I can do that more effectively if I manage my exhaustion by take breaks when I need to.