I accidentally deleted your comment above! UGH... SORRY! Here is the answer to what you asked!
I don't know why I do this to myself. But I think it's important to recognize that it is just me doing this to myself. I haven't had any kind of accident. And I can trace it back to the EXACT DAY THAT THIS BEGAN. I tend to be anxious about all kind of things, my health being one of those things. I obsessively check my pulse, my blood pressure, by blood sugar. (I am not diabetic.. yet... here I am with a monitor..) Anyhoo.. For some reason that day I felt as I was obsessively monitoring my pulse after some moderate exercise, that a panic hit me, I suddenly thought my heart was racing (it wasn't before I panicked, I know because I had a fitness gadget with the heart rate display..) But in my mind I was checking my heart rate and thinking it was going to kill me. And then my heart WAS racing. I actually went to urgent care. They said it was sinus tachycardia which was caused by the panic attack. I saw a cardiologist and he could find not a thing wrong with me.
Have you ever felt your mind pull you into a panic? I can always feel that happening. So that's that. Just my getting into my own head!