Good nervous system recovery gives you the extra 10% not just for training, but for life in general.
You know those workouts where you feel sluggish, heavy, or unfocused for no good reason? If you're not actually sore or otherwise physically depleted, inadequate nervous system recovery could be the culprit.
Your nervous system, which controls all aspects of your movement and coordination, can become fatigued and under-recovered, just like your musculoskeletal system can. While poor nervous system recovery might be harder to pinpoint than garden variety muscular soreness, its effects on your ability to move well and train efficiently are no less detrimental.
For optimal function and recovery, your nervous system needs the ability to seamlessly switch between sympathetic activation (you're amped up and ready for action!) and the parasympathetic state (calm, relaxed, and easily able to drift off to sleep come bedtime). Ideally, you have access to both of these states at the relevant times, AND are easily and appropriately able to flow between them.