I find it hard to believe that happiness would be just a stagnant state or a goal. I'd say it comes from succeeding in things and seeing the world + your peers in a more positive context.

For example, I find challenging myself (or going outside my comfort zone) often very pleasing. Obviously not succeeding nearly every time as I thought I would but still happy I went for it. It's never comfortable but at least I know I'm alive and it feels exciting.

When I talk about fighting depression I mean measures to turn around the negative development. And you're right, it's about creating positivity in ones life but I fail to see how the change would come on its own.