Smiles are contagious, don't be afraid to smile to strangers. They will most likely smile back and who knows, they might even pass on that smile to another stranger.
Smiling can trick your brain into happiness — and boost your health. A smile spurs a powerful chemical reaction in the brain that can make you feel happier. Science has shown that the mere act of smiling can lift your mood, lower stress, boost your immune system and possibly even prolong your life.