Recently, my grandfather passed away. Losing him has of course had a profound effect on the whole family, but my 4 year old brother has been having a particularly tough time dealing with, and wrapping his head around what transpired.
You see, there's this happy little grace period at the beginning of any and all lives; during which the concept of death has not yet been forced so violently into the mind of an individual. My little brother has just been pushed over the edge. The other night I was settling him and he asked me when my birthday was. I replied and he asked me whether there was some way to avoid it because he didn't want me to "get older and then die like grandpa". He's also explained on multiple occasions that he fears turning 5 for the same reason.
Of course, whenever he voices one of these concerns we all do our best to comfort him. My most recent method for doing so was to count all the way from 1 to 100 following the statement "I am now going to count every year a human being is supposed to live". He seemed satisfied with what he'd heard, until about 5 minutes later when he asked "did you say supposed?". And so, the concept of death continued to weigh heavily on his mind. A week later, we were eating breakfast and he asked me why we try to stay alive if we're going to die anyway. I responded by telling him that if we weren't going to die, there would be no reason for us to do anything. I waited 2 minutes, then 5, then 10, but he was silent.
You only truly start to live once you realize that you're going to die.