Stress is something that affects many people in Cambridge, and not just during exam term. It can be something that affects you positively, making you more productive; or it can affect you negatively and prevent you from working and living properly. Stress becomes a problem when the latter is the case, but can be released, or dealt with in many different ways. Communicating your stress to a friend for ten minutes is usually a good first step, and finding ways to be able to take a break is the next.
Being over-stressed often has a lot to do with your environment and can sometimes be helped by putting your work or exams into perspective and reclaiming your own expectations rather than trying to live up to other people's. It is great to aim high, but none of us can be perfect all the time, and even then, your exams are only a small part in the grander scheme of your whole life. Many things will affect the course of your life, these exams are only one of them.
Different people find that different things help them with their stress. The best thing to do is try those out that seem most appealing to you. It is of course important to keep healthy and sleep well. Some people do exercise, some people cook; focusing on another skill, or something you're good at can often do the trick. By focussing on another activity you can ensure that you will really give your mind a break from your current assignment or up-coming exam.
If your stress becomes overbearing and persists, then you may want to seek help from your tutor, the welfare officer or other welfare services found in the contact here.
CUSU Exam Guide
Guide on university regulations for extenuating circumstances and disability allowances.
University Counselling Service Exam Guide
UCS's guide to exams and revision, including suggestions for dealing with stress.
BBC article on what stress is, its affects and how to deal with it.