"Scientists have proven that putting a smile on your face, even if you don't really feel like it, actually improves your mood," says Dr. Elizabeth Berger, a child psychiatrist and author of Raising Kids with Character. Besides, seeing the glass as half full is "a lot more fun" than the opposite, says Berger. "The New Year is an opportunity to start things afresh, and there is no better way to celebrate a new beginning than to promise yourself to fully savor the pleasures that are present." (As this 1944 photo shows, even during World War II, Americans celebrated in Times Square.) Read on for 11 reasons to be bullish in 2011.