He who does not wish to die cannot have wished to live. For life is granted to us with the reservation that we shall die; to this end our path leads.
Seneca, Epistle 30 (Gummere translation)
It is a strange thing - perhaps even a sign of a kind of madness - to expect or wish for something that cannot be. No man is so unstable as to be offended when one plus one equals two instead of three; or to lament that gravity causes an apple to fall downwards from a tree and not upwards; or to expect a rain cloud to produce sunshine. These are things that must be, ordained by the very Universe itself.
How foolish, then, that a mortal would wish to live forever! He torments himself, desiring the impossible, while neglecting the possible - to live life nobly while life still remains to him. This one thing should be his desire.