One bit of trouble (of many) is that there's tremendous pressure to act happy even if you're not. People rarely react well when you act the way you feel, if you're feeling like that. People often take it personally.
They get upset at
you for not being happy. They think they've done something to make you unhappy. They feel at fault, even though they're not. It's easier to put up an act than just be yourself.
I think a lot of this comes down to a very poor understanding of mental illness in the general population. Nobody has a problem if you can't play frisbee with your friends because you broke your legs. But if you don't want to play frisbee with your friends because you brain is sick, their frame of mind is completely different. They're not thinking of it as a disease, with your mental state being just as much of an uncontrollable symptom as the inability to run is out of the control of the person with the broken leg.
We need to better educate people on this stuff. I'm sure that discussions like this help, as long as they don't go off the rails into misinformation.