You're wrong about not being able to live happily ever after: It's never accepting you'll be forever unhappy -- it's accepting you can't be without aid or intervention (e.g. medication, therapy, etc). I never stated that they're doomed to feel depressed, just that they're doomed to feel depressed if they don't do something other than sit and think. Depression tends to lead to a lot of rumination anyways, so it probably will seem pretty ridiculous to them to be told to be more introspective.

To clarify, I put those (schizophrenia, homosexuality, transgender) as examples of brain structure and wiring (just like clinical depression) and mentioned homosexuality explicitly because it seems less stigmatized than mental illness currently. A gay person can accept being gay and live a happy life, but they can't think themselves into being straight if they try hard enough. An individual diagnosed with major depressive disorder can accept they are clinically depressed and require treatment, then take the treatment and live a happy life, but they can't think themselves into not requiring outside aid to be in a non-depressed state. Society is a lot more accepting of the gay person than the depressed one though.