Children joyously enjoy every moment as if it is their last, this is true understanding of death. They act as if things can only get worse and they are right. Emotional pain, such as seeing other's deaths, imply a future worse than death.
Only when light as air itself can one live without respite. Any burden at all eventually will force the perspective of living life through the lens of "Are we there yet?" (Or more modernly, only when light as a photon can one reach the speed of light and negate time.)