If you want to know what makes you happy, you have to be willing to think hard about what happiness is, and pay attention to what makes you happy.
"Happiness comes in small doses, folks. It's a cigarette butt, or a chocolate chip cookie, or a five second orgasm. You come, you smoke the butt, you eat the cookie, you go to sleep, wake up and go back to fucking work the next morning, THAT'S IT! End of fucking list!" - Denis Leary
So after much time and experience, here's the list of things that make me happy.
1) Direct sunlight.
2) 8 hours of sleep.
3) Movement outside.
4) Social interaction.
5) Regular meals.
6) Satisfying work.
The upshot from this list is that I'm not all that complicated. Also, what actually makes me happy may not be what I spend most of your time thinking about. I don't think about sunlight all that much. But I can tell the difference between when I have it and when I don't. Biking has a huge effect on my mood. Not eating has a huge effect on my mood. And I'm going to take a leap in logic and say that this list is globally applicable to all humans.
The complicated part of this is social interaction and satisfying work. But even the satisfying work is simpler than you might expect.
But hang on a sec. This list doesn't just apply to humans. Look at dogs, for example.
Dogs need sunlight. Just ask one.
Dogs need sleep. They get cranky if they don't.
Dogs need walkies.
Dogs need to meet other dogs and sniff each others butts. And humans.
Dogs need regular meals. And they'll eat anything you give them.
Dogs need to do something. Pointers need to herd, bloodhounds need to sniff.
You break it down and you'll conclude that human beings are social animals, and have the same needs as social animals. I used to think that the people who get up at 8 am, eat breakfast and then jog for an hour were obnoxiously happy people who were just naturally gifted. They're not. They're happy because doing those things will make you a happy human. Likewise, staying up until 3 am, not getting outside, getting crappy sleep and reading existentialist philosophy will make you pretty damn unhappy. It doesn't matter what your brain thinks about the activities you're doing -- do these things and you'll look and act like an unhappy person the next day.
Again, this goes back to how to get the most milk out out of cows or the most work out of programmers.
The Dog Hypothesis: Human beings need walkies.