You know what I noticed about Jerry Seinfeld lately? The guy still LOVES the joke. He loves the entire process of writing them, hearing them and performing them. Despite his amazing success and the knowing of the science behind the joke he remains childlike in his quest for funny. Have you ever took a good look at Seinfeld's face when he's hearing a great joke or he's in the process of thinking about some part of the setup-punch line? You can see the kid in him come to the forefront. That guy is in line for the first seat of a roller coaster!! Comedy is his light and youth serum I'm thinking! He LOVES it!
But you know what? That's the kind of passion you GOTTA have for stand up to succeed. I've seen that light thing before on other famous comedy faces. I know that's the light of artistry, it's the magic, it's the drive and why we do this crazy thing. You GOTTA have it. And I know it when I see it. ;)