I don't think it's a switch at all. It's something going on inside of people all the time. But we learn to hide it. We learn not to talk about it, because you're not supposed to talk about it. Because people tell you to cheer up, to be happy for yourself, to count your blessings.
So quietly, you suffer, and you go on, every day, because you're supposed to be happy, and you're supposed to feel satisfied, and all this success is supposed to mean something, but you just feel empty and worthless inside, and you know you don't deserve it.
Depression doesn't care if you're rich or handsome or powerful or popular or surrounded by people who worship you. Why would you think it does? Does diabetes care if you're rich? Does cancer care if you have a TV show or a bestselling book?
We still don't take it seriously as a disease. We say, "How can someone with such a life be depressed," because we still think, well, they should just *choose* to be happy. As if people wouldn't choose that option if they could.
All you can do is just try to manage it. And sometimes, you lose that battle. Sometimes, the depression just wears you down, and you're so tired of feeling so sh!tty, of feeling like nothing matters, of feeling like you're worthless and unworthy of love, that you'd rather just not be alive anymore.
But please don't view it as a reflection of who these people are. It's not. It's the disease.
Get help if you can. Go to therapy. Get treatment. It can help. It's helped me.
But it doesn't help everyone. And we need to look at it honestly as a disease.