I would remove the ability to become physically or chemically injured before the age of 100. If no one could die before they were "due" then most fears are basically eliminated. My hope would be this sudden loss of fear, but keeping the inevitability of death, would eliminate hatred or racism. If you cannot physically harm someone, then you cannot "beat" them in this biological rat race we call life. If you are guaranteed to die, but only after 100 years of life, then you still are forced to make your time count for something. (I through chemical injury in there to negate poisons and genetic disorders such as Alzheimer's).