The level of cortisol in the body tends to diminish in the presence of positive emotions and achievement – appropriate play provides both, while TV and video games provide little of either. (Hartmann, Thom. The Edison Gene. p 129-130. VT:Park Street Press, 2003.)
Strong emotion fixes specific moments in the memory; you are more likely to recall those times of strong emotion. Emotions can also amplify an experience. (Ornstein, Robert. Multimind. p 106-109. NY:Doubledday, 1986.)
Refer to Emotions and Feelings for additional information.