I'm a huge cardiac worrier for as long as I can remember. Had every test that they can give me short of surgical exploration. Everything has come back fine. But I still worry.
What finally helped me was the realization that if everything I've ever thought was a heart attack actually wasn't, then - God forbid - if I ever actually do have a heart attack its going to feel very different from anything I've ever felt. So, as long as I keep having the same old symptoms I don't worry about it.
If something new does pop up, I calm myself down and ask myself this question - "Do I actually think I'm having a heart attack or am I just worried that I'm having a heart attack.?" The answer is always "Worried" and I go about my day.
As one doctor told me - when it happens you'll know it.