I was often told to smile when younger, not often now, but still sometimes. My face often looks "blank" which is often mistaken for unhappy. Usually, I am just concentrating, or lost in thought, or daydreaming, or tired. When younger, my eye brow shape tended to make me look angry, even when I wasn't, and even more so when I was concentrating, as the brows draw together more then. Over many years, I have been working on reshaping my brows to make them less "angry" looking, and also to minimize a tendency to be "clown" shaped brows. I think it has helped fix both those problems, however, the blank look is still taken as "unhappy", but I can't fix that.
Although I am not deaf, I look at lips while conversing with people. I have difficulty looking other people in the eyes. It makes me extremely uncomfortable, and feels so wrong and unnatural. I also find looking at their lips while they speak seems to help me input and process the conversation better.
If someone tells you to smile, just tell them you are not unhappy, just concentrating hard on the conversation because of a hearing impairment.
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If a man does not keep pace with his companions, perhaps it is because he hears a different drummer.
Let him step to the music which he hears, however measured, or far away.--Henry David Thoreau