Here is a lesson I took many years to learn:
Set a Personal Record, Go Home.
Last Monday I set a PR for single-leg box squats.
Today, I did the same exercise and set a 10 pound PR over the previous lift.
I had more left in the tank. I probably could have gone for a 15-20 pound PR after that.
I didn't. I put the weights down, did a bodyweight squat set to ensure I was still going strong and well, and quit.
My next leg exercises were all the same as last week, which was the same (or in one case, a little less) than the week before that.
The reason is pretty simple - a personal record is a record. It's a weight I've never done before. I will adapt from that. I will get stronger. Why risk injury or overdo it or otherwise pile on in the hopes of eking out a little more gain?
I was sure to go home with gains.
That's what I did.
It took me a long time to realize that all I needed to do was ensure a gain, not try to maximize each workout.
Hopefully this post will help other realize this a few years, and a few injuries, and a few setbacks, earlier than I did.
Work hard, set a record, and take that record home with you.