Now that I think about it: Life is the pursuit of the perfect balance of control and wonder shared with other people. Just 3 items.
I got that from combining some of the terms in a past post:
-optimism is simply control of mental facilities perceiving future growth
-purpose is again control of perception of future worth
-challenging work is the wonder of surprise (not knowing if you're succeed)
-fun is fun (the balance)
*and the crux is having friends in close relationships; sharing
**So, this is it: the pursuit of happiness!