Simply Stoic: Chapter One of On the Shortness of Life by Seneca

People complain because life is too short and that short span goes quickly. Everyone, rich and poor, famous and common, bemoan this fate. Hippocrates said "life is short, art is long." Aristotle, contemplating the subject, said Nature must favor animals as it gave some lifespans far longer than ours, forgetting that at least we are capable of greatness. It isn't that life is short but that we waste it. Life is long enough, provided we spend the time wisely. Used carelessly and you won't even notice that life has passed until it has. So, it is not that life short, but is made so by our foolishness. As good money can be used poorly by wasteful people, so too can a good life be used poorly. Just as poorness can become greatness in the hands of wise, a poor life can become greatness when lived with wisdom.