IWTL how to speak in awkward conversational situations.

I tend to freeze up during awkward conversations. My default face is not a smiley one, matter fact its probably more of an apathetic/unsmiling/mad looking face. I think i have a pretty good smile but when it comes to awkward social situations, and i start thinking about how i look, i end up freezing up and not smiling => default face(no good for non close friends)

EDIT: the question was meant to be more like "IWTL how to smile while speaking in awkward social situations"