When I went through my depression, I did some reading on it, and this comes up in the literature. Essentially, people who struggle to feed themselves don't get depressed. Depression is a first-world problem because we have the time and luxury for introspection and contemplation.

A large part of what got me out of my depression was making meaning for my life. Discovering what really matters to me, and living my life by my discovered values.

I'm also, now, easily the most optimistic person in my peer-group (I definitely was not before). I believe the world is getting better every year, and that the human race will rise to overcome all the challenges presented to us.