The closer to your limits you push, the more stressful it is to your system. Not in a "I'm under pressure" way. In an endocrine system, hormonal way. Lower reps call for heavier weights, closer to your limits. When you stack these heavy sessions together, it can be a lot to recover from. The stress hormones build up, and it effects(affects?) sleep. Next, it makes you irritable during your daily life. Then you start getting all emotional. All signs that you're pushing too hard, too fast.
This is what happens to the Bulgarian weight lifters. For every Olympic champ, 1000 dudes get burned out and crushed by their system. Most of them get ground down emotionally/ mentally.
For awhile I got on a routine of working to a 5 rep max week 1. Then a 3 rep max week 2. A new 1 rep max week 3, and a week 4 deload. I peaked the weights on assistance exercises too. It was cool for awhile. Every month you could count on a whole week of pr's, every lift, every day.
Before long, it crushed me. I couldn't sleep through the night. I was moody. I started loosing muscle and getting little injuries all the time. Little man went into hibernation. It was awful.
When I train a little lighter, and progress a little slower, I can avoid these issues. Sleep problems are the first sign I need to back down a little.
More sets around 80-85% have been working better than less sets with 90-95%.