Somewhere between checked out and freaked out lies an anxiety sweet spot… in which a person is motivated to succeed yet not so anxious that performance takes a dive. This moderate amount of anxiety keeps people on their toes, enables them to juggle multiple tasks and puts them on high alert for potential problems.
– re-quoted from David Kanigan’s Blog: Lead.Learn.Live
which was, in turn, from WSJ.com: Anxiety Can Bring Out the Best
[Very reminiscent of the comments made in the book: Future Shock by Alvin Toffler. Although there, the accelerating rate of change being brought about by the future (actually, increasing volume of changes in the present) was what was causing the increased anxiety. -- KMAB]