Thanks to technology, we live in a world that's much more comfortable than ever before. But here's the paradox: our tolerance for discomfort is at an all-time low. And as we wrestle with a sinking "discomfort threshold," we increasingly find ourselves at the mercy of our primitive instincts and reactions. Designed to keep us out of danger, our limbic brain's survival instinct controls what we intuitively do to avert injury or death. Rarely are we...