So how are we supposed to know if we're doing too much or too little?
Author Dave Navarro mentions in his manifesto More Time Now that we just have to ask ourselves the following question.
How many things do you regret not having accomplished, attempted or experienced over the last ten years?
Answer it honestly, and you'll know just how you're doing.
Picture from http://cutcaster.com/photo/800895787-time-passing-clocks-and-gears/