I have this problem, smiling at inappropriste times. 3 or so years ago I had to a funeral of a relative and I barely held it in, don't think anybody noticed, back then I had more control over it. Had to carry the coffin as well and was pictured, would have been disasterous. Right now I don't think I could do it. My grandma's health is poor and not going to the funeral of your grandma who basically raised you is not an option. O well.