It sounds like a habit to me. As if he's gotten into a habit of not smiling and now to go around smiling would feel weird. He's too much of a sourpuss to notice the sweetpuss...wait, I'll stop.
Have you ever read Michele's book A woman's guide to changing her man? It's a good read and includes the SBT principles that you see over and over on this website. Basically it would advise you to get him to smile more by positive reinforcement..noticing when he does smile and complimenting him on it. ("I love it when you smile like that", etc)
I found it at the library and wish I did more of the principles in this book and less of my tried-and-true-flop stuff!
