On The Shortness of Life

De Brevitate Vitae (English: "On the Shortness of Life") is a moral essay written by Seneca the Younger, a Roman Stoic philosopher, sometime around the year 49 AD, to his father-in-law Paulinus. The philosopher brings up many Stoic principles on the nature of time, namely that people waste much of it in meaningless pursuits. According to the essay, nature gives people enough time to do what is really important and the individual must allot it properly. In general, time is best used by living in the present moment in pursuit of the intentional, purposeful life.
In the treatise Seneca argues that we waste so much time because we do not properly value it. We expend great effort in protecting other valuables such as money and property, but because time appears intangible, we allow others to occupy it and take time away from us. Wise people, on the other hand, understand that time is the most valuable of all resources, and with effort can free themselves from external control to engage in meaningful introspection and create an intentional life.
Seneca urges his readers to live in the present, and adapt themselves to a purposeful life in agreement with nature. Only by doing so, can one then truly unlock both past and future. The completeness of each present moment allows one's awareness to expand to the equal of that of the universe, and achieve true virtue and happiness.