Many colleges and other groups run relaxation classes. It will help release tension and enable you to relax. Make sure that you get a balanced diet. Don't miss meals because you're working too hard, or because you don't think you can afford to. Life at Cambridge is undoubtedly stressful.
Short terms add to the pressure on everyone to compete and succeed, both socially and academically.
Before you come up it is easy to believe that Cambridge is a kind of wonderland where no-one could possibly be bored or unhappy or lonely. Finding out the mundane reality can be a shock to the system. The knowledge that feeling depressed is common and not a sign of inadequacy is a step towards coping, should a crisis arise. A period of depression, if seen as a failure, can be the start of a downward spiral from which it becomes difficult to regain confidence. Depressive moods can result in wasting enormous amounts of time and energy.