I grew up in a low-income family with alcohol problems and lots of stress. Somewhere along the way I started dealing with my family and myself by using laughter as a coping and denial mechanism. As I matured and began dealing with myself in a healthy way, I kept my sense of humor and it developed into a communicative method with others, to convey a sense of hope and positivity.
A lot of people in the world live mundane or difficult lives, life can be very hard and there is much tragedy. But if we use smiling as a way of conveying hope, and seeing the good in each person, then it is not the pejorative Polyanna (http://en.wikipedia.org/wiki/
Pollyanna) optimism, but more of the Christian philosophy of seeing Christ in every person. This is not false "happiness" but the ideal of lifting people out of there own shameful mire.