Co-worker: "...I don't think I can picture you not looking happy."
I put myself through a lot of stressful hell to get through my Number Theory class last semester. I cried, I yelled, I railed against my own lack of care (I wound up with a B+, because I worked hard and put a process in place.) I certainly wasn't looking happy then. In the last year, I did a lot of mourning of the opportunities I have chosen not to pursue because I decided to father Melinda. I was crying and whining and not terribly happy then.
But, I think he was on to something. In a few years at work, I've gone from 'People don't know how to approach you, you have no tail' to 'People are coming to you all the time for advice and help, and you're great at interacting with our customers.' Somehow, I managed to solve at least some of the social puzzle without trying too hard. I have a job that is technically rewarding and socially invigorating. I have a daughter who is rather attractive and developing normally. I have a wife who is so incredibly loving and supporting, and who I get to support in very real ways. And I have friends of just about any level of intimacy when I want them. Why shouldn't this man be smiling?