That's why I give little credence to ideas like those in your link. I don't consider the worldview of depressed people to be valuable to my own life experience.
My link is also not arguing for being depressed. Once you are here, by all means make the best of it. But to give you all a flashback to sex ed, do the right thing and use a condom.
Self-sacrifice occurs in animals too. From what I've seen, it isn't controversial.
What if there is?
Generally, we are not very good at judging what makes us happy. Happiness research points to things that many of us are indeed missing in life: physical activity, social connectedness, interacting with nature.
The reason for unhappiness might also be internal; bad diet, lack of exercise, etc. throws your body's hormones off-balance, making you feel like crap and causing, quite predictably, unhappiness.
They can certainly help a bit sometimes, just like not punching yourself in the face every day while you have a broken leg helps with the pain and makes recovery go more smoothly. But it is not a solution to the underlying problems in many cases.
These things are important to everyone's wellbeing, but there are many, many people who eat like crap and don't exercise who are not clinically depressed. And there are plenty of people living with depression despite being disciplined in these important lifestyle choices.