I'm very cynical and see life as generally unjust and unfair, of petty people living in an indifferent universe. People say I'm too cynical, but usually when I'm wrong it's because I'm not cynical enough.
Nevertheless, I generally have an easygoing attitude toward life, and knowing how bad and dangerous life can be makes me thankful for what I have. I could worry about all the bad, but it's not a burning issue for me, though I do take what I consider reasonable precautions. I laugh and generally enjoy life, though there's an element of fatalism to my optimism. But I have to be careful about what I saw as it's too intense for others (perhaps my saying it casually or even with gallows humor only makes it that much more disturbing).
I also feel lucky to born in this time of history. I believe that we're at a pinnacle of civilization, that as bad as it may be today, it can only get worse (at least for the developed nations) and that it will only last while the resources are such that it's better for those at the top to use consumerism (and allow technology to generally make life easier) rather than brutally fight over resources as used to be the norm (and still goes on today to a lesser extent). (Sure, better models exist that could make the world radically better still, and for a long time, but they will not be implemented.) Well, things can be tweaked for the better still, and so strictly speaking I actually think we're starting to crest the pinnacle (without actually having reached it), and I think there are decades at least before humanity begins its downward spiral (but again, when I'm wrong is usually because I'm not cynical enough).
I think the key element to happiness is not to feel too entitled (not to say that people should be apathetic and spineless). If people take the good for granted, and also expect all sorts of benefits, then they become miserable, and worse, when life isn't all that they feel it should be (and sometimes gets called "first world problems"). It's been like this for a long time, as I've read of history where feast days were times of great joy for villages while rulers, used to luxury, found feast days dull and unexciting. The poor people didn't take the good for granted and generally had a better life because of it (though of course tyrants could easily rain on their parade, but the elements themselves were the biggest tyrants--having heard many people say they wish society just collapsed and they could live off the land, I'm convinced they have no idea what farming would be like without modern technology and the infrastructure in place, let alone what many power plants would do without maintenance).
Oh! And I have to add this. It's from a review of a Buffy episode, but I want to cut straight to the end which quotes Stanley Kubrick:
https://youtu.be/KiJ7Kscpyks?t=6m6s