In my view, the balance between stress and contentment was life's biggest riddle. On the one hand, I was utterly convinced that the continuation of any success I had achieved was contingent upon persistent hypervigilance. I figured this kind of behavior must be adaptive from an evolutionary standpoint--cavemen who worried about possible threats, real or imagined, probably survived longer. On the other hand, I was keenly aware that while this kind of insecurity might prolong life, it also made it less enjoyable.