Since I occasionally sing in public, I try to remind myself to keep eyes open and in contact with the audience. It feels natural when singing a peppy or raucous song and you have a smile on your face. The opposite seems to happen on a slow moody one. Sometimes I will have my eyes closed on one of these, remind myself to open them, and actually have one pair of eyelids almost locked, which must be an indication of how intensely I was trying to emote in the song. Anyway, it has to look fairly weird to the audience.