Happiness is interesting... I find that more than anything, it's a mindset, a choice. One can choose to be happy through some pretty dire situations, or one can choose to be unhappy through things that aren't really a big deal at all. And of course, I mean "happiness" in a broad sense-- overall satisfaction with one's life-- rather than the situational, day-to-day mood. I chose 8-- I'm overall very happy, but that doesn't mean I don't have days when I'm just down, or that I get sad when sad things happen. But even during those times, I would still say that though I may be sad at the moment, overall, I am happy.
At the moment I have a pretty significant source of stress and sadness, but I don't let it take over my life. I've had a few days lately that weren't very happy, but all in all, I've got it pretty good, so I'm not going to let one aspect of my life (even though it's a huge one) negate everything that is good in my life.