Physical exercise is the answer. Not only does it channel and exhaust stress responses, it also diminishes one's reaction to future stress by conditioning relaxation. Those who keep fit generally reap the rewards of mental alertness, good self-esteem and fewer spells of depression and anxiety. Even exercising during the next 24 hours will help. Although exercise is a form of stress in itself, the muscular, respiratory, metabolic and central nervous system react positively to exercise, strengthening one's ability to cope.
Regular exercise is especially beneficial.
Rather than wait for psychological stressors to trigger destructive stress products, the individual involved in regular exercise uses them up daily. In a game of squash where your ego is on the line, you will not reap all the benefits that exercise can provide for your psychological well being. You can't expect to feel internal calm when you wrap your golf putter around a tree in a competitive game. But man is a competitive being with extraordinarily developed competitive instincts. You know you are on the wrong track when you pursue physical exercise with the same zeal and competitiveness with which you pursue your work.