Training "on the nerve" is a mindset many lifters put themselves in before the lift or set begins. You should limit the number of sets that you need to psyche up for. This does NOT mean a great deal of concentration isn't involved. It's the opposite.
Remember that cortisol is a stress hormone and it's part of the fight or flight response initiated by the sympathetic nervous system. When you work yourself up into a frenzy before a set (which isn't even required to lift maximally heavy weights), you stress the adrenals significantly time and time again. This is stress on the sympathetic nervous system.
However, it's the parasympathetic nervous system that aids in recovery post training. And of course, training causes stress to that system. This is why when we talk about recovery, it's important to understand the difference between localized recovery (at the actual muscular level), and recovery at the systemic level (the various nervous systems).
Training on the nerve too often means there's going to be a significant downward curve of the nervous system. When training is intense, the PNS becomes suppressed and power output diminishes. Despite all the talk about "CNS" recovery, it's the SNS and PNS that are most involved in training. To stay on top of your game, keep to a minimum the amount of sets you have you have to "psyche up" for.
Your biggest sets shouldn't have you screaming and yelling all over the place like a madman. The majority of the greatest lifters approach the bar in a Zen-like state of concentration. Sure, there are a few guys that get crazy, but moving your biggest weights should require focus and concentration, not acting like you're on PCP.