Just because people have challenges, it doesn’t mean they are unhappy. Challenges could be temporary setbacks or you could find happiness and contentment in overcoming challenges.

It’s possible that you’ve never met happy people because you don’t know them on deep level as you don’t have close friends. You simply don’t know enough people not on superficial level to determine that everyone is unhappy. The fact that you don’t know happy people, doesn’t mean that there are no happy people. Just that you don’t know any.