Just read for the first time Bertrand Russel's In Praise of Idleness. I recommend it for anyone who hasn't shaken the notion that they must be productive at all times to justify their existence.
Which may seem like an odd statement from someone who has a goal to help 100,000 people to manage their time better, but is actually completely consistent.
I know a few tricks to help squeeze more out of the time you are already spending working, but that is to free up leisure time. It is in this leisure time that reflection occurs, and priorities get reevaluated, even in miraculously short amounts of time. When I first started experimenting with the pomodoro method, I found that during my 5 minute break period, I would often realize that I was either going about my work the wrong way or working on the wrong thing. If you stay locked in too long you're actually a much less effective worker, let alone less effective at the work of living a good life.