An interesting and provocative question. I don't really know what makes people in general happy, I can speak only for myself, but I'm inclined to think it's a byproduct of other things, not something you can go after directly. If you have something interesting and useful to do, enough money to be able to stay warm, clean, dry, fed, and clothed, if you know you're loved and valued by family and friends, odds are you'll be happy. If you don't have those things, odds are you won't be happy.
I've been unbelievably fortunate all my life with those things, and I'm one of the happiest people I know. My life so far has been one of extraordinary comfort and privilege, and a lot of that's due to nothing more than the fact that I'm a white, English-speaking, university-educated heterosexual male born into a prosperous upper middle class family, living in a time and place where those characteristics put me on top of the heap. I had nothing to do with any of those except the education, for which I had to pay the tuition fees and do the work, but part of the reason I was able to pay the fees was because I'm a white, English-speaking, etc. My life of comfort and privilege I've done very little to earn, it seems almost entirely accidental to me.
So now in retirement I'm trying to give some of it back. I've just signed up with Habitat for Humanity and I'll be spending much of the summer swinging a hammer on behalf of people less fortunate than I've been. And that too makes me happy, because it's another something interesting and useful to do.