8. Engage in frequent introspection, or at least look like you are.
If you look just behind Don's well-maintained facade, you'll notice there is always something percolating just below the surface. You see it Don's drawn out stares into the darkness and hear it in his silence. When Don slips out of his daughter Sally's birthday party, and we see him parked beside the railroad, after he's hustled by two hitchhiking teens, we see him quietly observing his bruised face in the mirror. Before he has his epiphany to send that bold-move letter to the Times, he's gazing into Midge's mess of a painting. What does he see out there? It's himself. In Don's loner moments, we see his rifling through his soul's contents, as if he trying to unpack some imporant truth.
It's this inclination towards introspection that endears viewers to Don, because it hints at the depth of his character. And while the other characters on the show aren't privvy to the all-access pass to Don that we are, Don carries this sense of self-reflection with him.
Live like happiness is fleeting, but maintain a contemplative quality that makes others wonder if it's true. They will find you intriguing, and they won't even know why.