Everything I know about Jiu-Jitsu a lot of other people know too. The difference is that I execute the same moves but without using force.--Grandmaster Helio Gracie, as quoted in "Extra fundamentals" by Raphael Nogueira, GracieMag
I don't have the vigor or physical prowess anymore but I'm still evolving, using less and less force, getting less and less fatigued. That helps me to subconsciously relax my muscles. You may try not to exert force by controlling it mentally, but if I poke you, you'll contract your muscles. Turning relaxation into something instinctual is a lot harder and takes longer to accomplish. I'm always relaxed, whether asleep or awake. Whenever someone readies for attack, his muscular contraction tgives him away and, since my reflexes are quicker, I preempt him and defend. No one catches me off guard.