It's also true that, in training, if you are constantly "emptying the tank" you will run out of gas and likely break yourself.
I know many who think that if you aren't nervous going to the gym, then you aren't training hard enough. Every session must be a battle. The brutal truth is that those people have more testosterone than brains and only some combination of youth, drugs, talent, inexperience, and dumb luck have kept them in the game this long. They are often the same people that believe that there is no such thing as overtraining, only under-recovery (and/or under-eating).