We are in the process of relaunching our CD, Signs, and I am reminded that Chris does a really nice bit on what happens when we push other people to give more than 100%. He talks about what happens to kids on the sports field when their parents start to yell "try harder." The harder they try, the more they miss. They miss the ball; they miss opportunities; and they miss the intrinsic joy of being fully engaged.
As human beings, we fully engage at some point where our minds and bodies still have some flexibility. We perform at our best when we still have some stretch in us. At 100%, we become uncomfortably aware that we have nothing left. Becoming aware that we have nothing left takes attention away from our actions, and so we drop down below 100%. It's a really useful feedback loop that automatically kicks us back into a place where we have the flexibility we require.
It's not possible to give more than 100%. When we try to push ourselves to give more than we have to give, we over-extend and over-commit and over-exert. None of these produces good results. We push past the barriers that exist not only to keep us safe, but to keep us at optimal levels of stress. We try harder instead of accomplishing more.