Smiling
According to article in the NY Times titled A Feel-Good Theory by Daniel Goleman "putting on a sad face or a smile directly produces the feelings that the expressions represent, according to a new theory of how emotions are produced." According to this research, a smile "affected the temperature of blood flowing to the brain, providing a possible, although disputed, mechanism for regulating emotions." And, smiling at others will typically result in them smiling at you too, w