My wife Karen and I have been going to the gym since October.
We did 10 sets of ring rows, 10 reps.
10 sets of weighted split squats, 10 reps per leg.
At what point does exhaustion over come gains?
I am 66YO today and whining. 
And unexplained. My hair is getting darker, no longer a blaze of white. Might be the training, or the body wash at the gym, or the seaweed we are eating or transdermal iodine. Will never solve this one.
If you fall asleep mid-rep…
What!?!?!?! Something Ksman doesn’t know about?? I thought you were the fountain that all knowledge came from?
Just kidding ya,
Stick with it, It will get easier and you’ll begin to enjoy it.
You seem to have figured out that 100 reps of any exercise is a lot! Perhaps you could do lower volume, but higher intensity?
You’re entitled to whine at 66. I whine and am still a few months from 50.
Hmm. Reps are not really my friend. Anything over 5 for me is cardio and no fun. And I’m all about fun in the weight room.
Probably shouldn’t listen to me, though.
And what a GREAT name your wife has!