A smile is a gift given to us by God.
A smile is highly contagious and has a tendency to spread from one face to other as a form of nonverbal communication.
Smiling affects our brain causing it to pump out more endorphins to make us feel happy and serotonin to relax us.
It has been proved in many studies that smiling can impact our mood and influence a great positivity in our behaviours, amplifying it even if we are not feeling cheerful at that moment. You are definitely better looking when you smile when you smile people treat you differently. You are viewed as attractive, reliable, relaxed and sincere. When you view a person smiling, you actually feel rewarded. So you should pass on this reward to others frequently. Sometimes your joy is the source of your smile, but sometimes your smile can be the source of your joy.
So smile and let your world smile :)