I found this talk from the TED Conference (circa Feb. 2004) about Flow (or being in the zone) very interesting. Dr. Mihaly Csikszentmihaly describes his findings (which make intuitive sense) on being in Flow, which “is the mental state of operation in which the person is fully immersed in what he or she is doing by a feeling of energized focus, full involvement, and success in the process of the activity.”
The following diagram breaks down the various states of being that we experience:

You’ll notice “flow” in the upper right-hand corner, tucked away next to Arousal and Control. What amazes me is that this is the opposite of “vegging out”, which (according to Webster) “is to spend time idly or passively”. And, I would argue, most people try to optimize the time in which they are vegging out, not in Flow.
This research suggests that we should look to spend more time in Flow, which means we should continually do the things that require a heightened sense of involvement and focus. This seems like a bit of a paradigm shift for most.
So perhaps we should all spend more time finding activities that require a great deal of focus, but give us that “in the zone” feeling instead of spending most our time passively amusing ourselves.