So how aware are you of your heart-rate?

I'm keenly aware of when my heart-rate rises, I notice it jump if I sprint up a stairwell. When it gets too high I can feel the pressure in my neck and temples. I'm the most out of shape I've ever been at this point in my life and I'm alarmed sometimes at how often my heart-rate stays high after seemingly inconsequential physical exertion so I'm wondering if it's something you tune out when you're really out of shape or overweight.