Why do some people always look at me with frightened eyes? My appearance is really ordinary. What have I done? Awkward.

Maybe there's nothing wrong with your appearance. For example, some people's fierce looks will make people feel scared, but they are naturally fierce and cannot be changed, but you can smile, which can be done. Besides, you should keep calm. Maybe others are just looking at others and you misunderstood, so there is no need to be embarrassed and smile.