I think people have to high an expectation from life. The whole point is to enjoy life and the people you hold dearest. Most people worry to much about money, looks, their contribution to society, is their job good enough, what other's think and are they popular or not. Stop trying to be or achieve the unatainable, enjoy yourself.
Idk but it sucks.
There is a genetic predisposition for depression. But then, there are social and environmental factors. I just think that we are too isolated these days and there isn't enough family or neighbour support. If we had (and participated) more in those, we will adjust better to our circumstances and possibly avoid some bouts of depression.
I've been reading the psychology books. Talking to others is the best form of therapy for all types of 'adjustments' (i.e. coming to terms with things). It is because you get other peoples perspectives and either empathy or a prompt that perhaps you views are a bit odd, whichever way it goes it helps. So without the family or social support I'd suggest finding lots of people you can talk to. I always recommend that you have people of your own age and gender, as well as someone a fair bit older (like an aunt or that age), if you are 30 or older, also someone younger. It doesn't have to be family, it can be church groups, or make friends out of colleagues.
Most people would be flattered if you said, "I've got a few things I'd like to talk about and to obtain your opinion, could you spare me 45 minutes over a coffee".
As a bit of motivation, I've had a big adjustment last year and everyone says how well I'm adjusting (and how quick, including the psychologist), I put this down to accepting my circumstances, and talking openly and frankly to lots of people, and listening to their responses. Oh, and I had depression in the middle of that adjustment.
Sometimes...it just gets to you.
All the damn changes on EP.