When you lose balance and fall off of a balance beam, you give up, you don't wait until you actually fall. When people become scared they do incredible things. I jumped out of a kayak in an emergency once without tipping it. I could never do that before or since. When people get demon possessed, their strength sometimes increases exponentially. Animal can do incredible thing with their small muscles. When you stop pushups, it's not because can go no farther. I believe that when we do something, we set in mental restrictions, sometimes in the form of doubt, which drastically decrease our output. I believe that God gave us some of these restrictions to protect our bodies.
Definitely; but then those restrictions are probably meant for our own good.