How to control high heart beat rate due to tension?

Stress reduction: If the high heart rate is really due to stress reduction, and you don't have an abnormal arrhythmia which can also be induced by stress hormones, then relaxation and stress management techniques should help. Also avoid caffeine, alcohol, tobacco, and stimulants, in order to minimize the stress response. See your doctor for evaluation to make sure it's simply stress and not something else.