considering your heart is maybe the most throbbing part of your anatomy i find it remarkable how well the normal physiology of man is set up to allow you to forget it exists until something is wrong, such that if you do become aware of it, the untrained default is to assume something is terribly wrong.
it has something of the Fall about it. I think Adam was constantly aware of his circulatory system and as we acquired concupiscence we had to close off awareness because it became too much