I get tired easily, and I have a higher than normal heart rate. Whenever I stand up I can get lightheaded and my vision goes dark for a few seconds. This doesn't happen every time but quite often. My heart rate can go up to 130+ just by walking to the kitchen to grab my phone. Sometimes I lie down and my resting heart rate is 90-100ish. I'm pretty healthy overall, no complaints other than that. I walk to work, I'm fit with a low BMI, low blood pressure, low cholesterol, etc.