Another symptom to watch for is shortness of breath, especially during physical activity or emotional stress. When the heart does not get enough blood, it cannot pump efficiently, which can make you feel breathless. You may also feel unusually tired or weak, even with normal activities.Another symptom to watch for is shortness of breath, especially during physical activity or emotional stress. When the heart does not get enough blood, it cannot pump efficiently, which can make you feel breathless. You may also feel unusually tired or weak, even with normal activities.