I like my job! I call myself a "technical engineer," because that's about as specific as I can get and still describe what I'm doing. I'm an EE by education, and I work for a small startup, doing everything from database administration to electronics design to firmware development to web administration to 3d modelling for some of our projects. I would say that there are a few things that contribute to my enjoyment: 1) the variety of work, so I don't get burned out, 2) proximity to home, 3) I'm paid ok, and 4) it's challenging and rewarding (look at this thing that I designed!).
When it comes to being happy, I think it has more to do with attitude than circumstances. Happy people don't necessarily fall into certain types of professions. Several years ago, I learned a really good lesson: "What you pay attention to, grows." If you focus on the negative stuff and complain about it, it'll become easier to find more negative things to complain about. If instead you take time to recognize positive things that happen, and make it a habit, you'll find it easier to recognize those things.