The most depressing job I had was only a 3 week job after I had graduated from college but before I left, so the summer after I graduated. I was going to another school in September and would be moving from the East Coast to the West Coast.
I was in the Appalachian Mountains and a friend had a summer job at Broyhill Furniture just down the mountain in Hickory, NC. He was driving down the mountain every day to go to work so he "invited" two of us (friends) to go with him every day just to make a little money at the end of the summer.
It was depressing because this was an old factory in a poor area and the factory looked like it had been built in the 1920's. The buildings nearby looked like company housing. The people that worked there were poor, uneducated, hated working there but it was the only job in town.
In the morning they would come in, sleepy, hungover, smoking and we had to stand all day by the assembly line. The furniture had already been assembled by the time it reached us and it had just come out of a spray booth where it was sprayed with lacquer.
This was August, there was no air conditioning, we had to stand all day and when the furniture moved by on the line, we had to use a rag, bend over and wipe some of the lacquer off of each piece of furniture as it moved by. It was totally a miserable job and most of the people working there had been working there their entire lives. At break time they would just lay on a nearby padded roll and sleep for 15 minutes.
At the end of the day they would walk home to smoke, get drunk, beat their wife and kick their dog only to have to come back the next day to a low paying job. It was hard not to have a headache all day just due to the working conditions.
I lasted the 3 weeks but if I had started at the beginning of the summer, I never would have stayed for 3 months, much less a lifetime of doing that.