Thankfully I'm not prone to stress, but one job I had was really horrible to the point I was getting very down and had to be forced out of bed in the morning. It wasn't a hard job, but I'm a sensitive soul and the monotony of answering phone calls to aggressive people every day took its toll.
I changed jobs and apparently there was an instant change in me (and I felt a LOT happier). This job doesn't involve talking to customers but is a much more stressful & high performance working culture. Time management and not taking work home with you I find very helpful, plus exercise is a great for stress relief. I very rarely find myself too stressed and find writing lists, and doing the quicker/smaller jobs first helps as seeing the list go down gives you a nice boost!