ATC is only stressful during training (college and unit) when you have to learn to operate to whatever standard/quirks your mentor may have. The training is tough and the standards are very, very high. And yes, I had a few quirks I'm sorry to say.
But once a trainee has his/her validation then the job is simply superb. Where else can you go to the same place of work and do the same job and yet have it different every day? I always compare ATC to golf, you are really just trying to do better each time.
Also, it is a service industry, I firmly belive the human persona gets a kick out of providing a good service. You can tell from the pilots voice if you've done well (or not!) and I always got a buzz from a busy session where I was able to provide a good service.
Stressful - no! What other job allows you to go to work without having to think of what you need to do to make your product more attractive/sell more/keep the company alive etc? I just talk to aircraft, many or few, then unplug and go home and not have to think about work until the next shift comes round. I think the average car salesman, or anyone in industry that has to plan and create a market, or with a job that is susceptible to market forces (like a slump) that impacts their salaries and ability to pay the mortgage, has far more stress in their lives than any controller.