There's a ridiculously vast difference between "a little fucked up" and serious mental illnesses such as schizophrenia, rapid cycling bipolar disorder or borderline personality disorder.

If you think serious mental illness isn't a real, debilitating reality, I encourage you to spend some time with somebody in a truly psychotic state and see how you feel afterwards. Then imagine living as that person.

There may be no absolute "normal", but there are most certainly people who live in a sad, terrible, frightening state of mental disturbance with no simple treatment.