If someone is fully aware that he has a limited life, it is not sure that he will try to live each moment of his life as intensely as possible. The unanswerable question ‘What I have to do?’ rises together with such awareness and often makes it inefficient.
And probably because the most certain realities cannot cause an action, but retain the man around them in a state either of prostration, either of delay.
For example, the most usual technical means of entertainment are all samples of what does really mean certainty, in spite of their complicated engines or functions, since certainty resides in the frequent and clear use of a thing. And many of them provide to their users various ways of delaying even the normal processes of thoughts and decisions.
The awareness of the brevity of life has the same consequences, though it should preclude any delay. On the contrary, it seems that when we keep some ignorance about the early end of life, we can live more efficiently.
For this reason, many preserve such ignorance by believing in an eternal life.