Seneca The Younger's essay to Paulinus, which covers his descriptions, observations and ideas about how short, frail and fleeting life is, and many of the people who are caught up in their busy-ness and inability to "unplug" from their ideas of self-imposed commitments, work, busyness, and when they discover that life is so short and frail.
The stoic teachings and observations of Seneca then, applies even more today in our modern world, where we're constantly bombarded with emails, ads, SMSes, demands...we need to slow down, evaluate what we do and live life more mindfully and meaningfully.
I personally have read and re-read this book and its contents multiple times, and each time I still enjoy the teachings today as I first read it before..
Best when read during quiet time during early hours of the morning, or late at night, or when traveling.