In my opinion as a certified "old fart" that's been around the block (and in more than one career) being happy with one's work is almost entirely a function of the individual, not the job itself.
The "more than one career" thing is the key. When I was flying a traffic reporter around one day, he commented on how his job sucked. I proceeded to circle a road construction crew that was digging a ditch, by hand, on a 92 degree day. He changed his thoughts of his job. I have driven all sorts of trucks, unloaded trucks, worked at a lumber yard, worked in an office at a mortgage company, and I can tell you, this is THE easiest job I have ever had. One day, back when I first started at JFK, an FO was bitching in the crew room about how this company took away his love of flying, how he did not even want to fly airplanes anymore. I looked right at him and said "Well, ##@ing quit." He did not know what to say, just sat with a dumb look on his face. I have always been upbeat and love coming to work. Things changed along the way though. This company has been so calous and uncaring about the way they are treating their employees with the displacements and furloughs that it is wearing on everyone. I have friends at XJet that knew 2 months prior what their furlough date was, and made plans accordingly. Here, they announced a displacement and furlough, then cancelled it, then reinstated it, all within a few weeks. Then they announced another displacement and cancelled it. Then, they announced the latest displacement, then a furlough list which furloughed many who were on the displacement list. It really begins to wear on you after a while.
When it comes to income, the income at a regional, even into the 4th year as an FO, compares to a full time job making $15-$17 per hour at any other job. Not much when you consider the cost of your schooling, the responsibility involved, and the other negatives of this job that others have mentioned. As I have said before on posts, I made 3X what I make now when I drove a truck. If it were not for this "heroine addiction" type love of flying, I don't think I'd be here. That said, I will be furloughed in January and may just go back to driving a truck. Or, I could just fly traffic flights, who knows.....maybe by then the judge will have Freedom cease operations for Delta, we will get all of our flying back at JFK, they will cancel the furlough and bring all the others back, and the whole thing will just seem like some bad dream.