In my recent book, I point out that the ever-adapting brain can take remarkable steps to trick itself into performing better.
Along those same lines, a pair of researchers in the UK are putting up the idea that smiling and sending fewer emails can make you feel happier—much more so than pharmaceutical treatments such as Prozac and other modern "happy pills."
Professor Janet Plant (an environmental geochemist by trade) and therapist Janet Stephenson outline their ideas in a new(ish) book entitled Beating Stress, Anxiety & Depression. I haven't read it yet, but they claim hard scientific evidence to back up what we already know empirically:
The mind is it's own place, and can make a heaven of a hell, or a hell of a heaven.
So the secret to happiness may be just that simple. Smile.