There's many things, but what makes me happy is:

-The DF parties with the sweetest people ever.

-Seeing the really sweet new/returning players getting excited with content. Things like, "Man, that was fight was awesome!" or "Did you see that? We crushed this trial!" makes me smile. It reminds me of the times when I was starry-eyed with nearly everything when I was a sprout myself.

-And...just having conversations with my FC members or friends