Feeling as if eternal
The psychology of this forgetfulness is rather poignant. In good health, we feel as if there's always a "next" day. Just as in natural numbers you can always conceive the "next number" no matter what number is given, in life it feels as if there is always the next day. In the finer scale, you feel as if there's always the next moment. Thus, in mathematical terms, a virtual potential infinity is incurred. The young and healthy can forget the inevitable death because they are living in the potential infinity.
Protention and retention are the basic building materials of our sense of the passage of time. It is interesting to speculate how the phenomenal experience of the specious present is somehow converted into an illusory feeling of eternity. In fact, it is probably the case that the very notion of the infinite or the eternal originated from the sense of potential infinity that accompanies the phenomenal experience of the psychological moment.
As it stands, thoughts about the potential infinity is not sufficiently separated from that of actual infinity. An argument must somehow be found which explains why a virtual potential infinity is incurred in the human psyche although in real terms the life span is necessarily very finite.
There is a potential infinity even in the course of a day, although in this particular case we have a cognitive process of imaging the "end of the day" through our past experience. It is the lack of the knowledge about when one's end is going to come that makes the potential infinity associated with the whole life qualitatively different from the one associated with a particular day.