Those people, no matter how happy they seem to be, all have their wounds. Some people can forget, some pretend to forget, and some choose to remember. Pretend to be happy
Those people, those who are truly happy, are also hurt. It's just that some people have experienced relief, and some people have seen too much and become numb and don't care anymore, and then become happy.
Those people, those who look unhappy, it's not that they can't be happy, it's not that they can't pretend to be happy, it's just that they don't want to be associated with this word.