I came across this quote by Lin Yutang in Zen To Done:
Besides the noble art of getting things done, there is a nobler art of leaving things undone. The wisdom of life consists in the elimination of nonessentials.
Update: This goes well with my post Turning 2008 into 80-20 which is about deciding what shall be done and what shall be left undone.
This was originally posted at another (now extinct) blog of mine.