I'd like to mention a few ways to avoid stress, if you fix the source of your problems then you can avoid quitting:
- Read Dale Carnegie's book How to stop worrying and start living (It's awesome).
- Go to a massage therapist, it helps you to relax and once more relaxed it's easier to eliminate stress.
- Prioritize and accept that not all things can be accomplished, but you can sure as hell do everything in your power to do the important things first and only think of those things until the less important things come at hand. One thing at a time and you'll accomplish more than you ever would have while being worried ! :)
- Exercise and change your diet. It's amazing how much energy it gives you which enables you to work even harder but yet it gives you a certain amount of releaf from your duties while exercising which is healthy and good to avoid stress.
- Cut out caffeine, I've heard of cases (managers) who have cut out caffeine and it has amazing power after about a week of not-using, it gives your body a better chance to rest when you actually need it and so fourth.
- Seek the help of a herbalist (I don't really believe in it myself but for some it helps).
- Take a vacation, with no emails and no cellphones.
- Study the interesting methodology of Mindfulness.
- Eliminate other stress factors out of your live that you do not have any control over (people, activities, etc).
- Take short breaks throughout the work day, especially when you've hit roadblocks and need to take a step back.
- Your employer may (check your employee handbook/with your manager) be fine with allowing a few minutes on your preferred social network site once in a while.
- Take a quick snack break once or twice a day (preferably with a healthy snack: banana, apple, etc. see change your diet above)
- Keep a journal (or start blogging). Reflecting on how your day/week went on a regular basis will help you deal with stress as you get it.
- Talk to your boss. Maybe he is assigning you too much work or there is a mismatch of expectations. He should help you prioritize your work.
If that doesn't do it, consult a doctor and or a psychologist to determine whether you're able to actually work at all.
If you're not able to work then I'm certain that they can provide you a medical certificate or whatever it's called which gives you the opportunity to quit without finishing your stay-time. Consult a lawyer if the company won't accept it.
If they can't, then I simply recommend that you talk to the HR and or your manager (what's the worst thing that can happen, you want out anyway?) and ask them to shorten your resignation-work-duration and you'll do what you can to ease your leave.
If neither option is doable, then I'd recommend that you simply resign and work those last months and try to take it easy (along with my advice).
The last option is to simply quit and don't show up again, but that would burn every bridge there is and you'd have a risk of being sued, so I advice you not to. Again, if you want out but you don't know how, hire a lawyer.