The excitement of reconnecting with God?
The happy-happy joy-joy of my life?
The sustaining of happy-happy joy-joy in other people's lives?
Fufillment of some pre-life training program?
Avoidance of after-life reprecussions?
Playing nice with others?
Continuance of a cosmic joke?
Because I have to?
Because life is a gift?
Sigh... none of these are working today. Maybe I'm forgetting something.