Dear madam Thanks for your query. A Hard beating of heart may come from stress/ anxiety and similar situations but normally it will beat faster too in such situations. An episodic isolated hard beating may come from pre-mature contractions. They can be picked up if an ECG is done at time of episode. If they come daily, holter monitoring may help. After determining the heart rhythm, ECHO should be done to look for structural heart disease. This will answer most of the questions. If there is no chest pain/ shortness of breath/giddiness/ vertigo/ loss of consciousness/ syncope/ presyncope associated with it, probably it will not turn out to be serious issue, but do get evaluated. Sincerely Sukhvinder