On the Shortness of Life: Life Is Long if You Know How to Use It by Seneca and C. D. N. Costa

Originally written around 49 AD for his father-in-law Paulinus, Seneca here brings up many Stoic principles on the nature of time, namely that people waste much of it in meaningless pursuits. According to Seneca, nature gives people enough time to do what is really important and it is up to the individual to allot it properly.