It is natural for anybody's heart to beat fast after some shock or tension. I would advise you to take it easy. Let it beat fast now; slowly it would subside. Do not take any medicines for it. Sleep well for as many hours as you feel comfortable. Go for a walk. Visit an old friend and discuss your problem. Even watching a good mystery, suspense movie would help you divert your attention for a few days. Deep breathing exercises of Yoga, meditation and prayers are known to control anxiety and its symptoms. This is an opportunity to learn how to cope with stress by yourself. You will most likely get over it completely in a period of not more than two weeks. If you still feel you are suffering, after two weeks, you may consider seeing a psychiatrist in person. Smile, this too shall pass...