It is a slow process and sometimes it is easier than others! If you definitely know that there is nothing wrong with you then you need to hold on to that. If you don't know, have it checked so that you are sure. I find that distraction is also great. I challenge the thought by: "I know this is a panic attack", "I know there is nothing wrong with my heart", "I have had this before and it has passed", etc. I also use distraction in between the thoughts, for example I practice dance steps in my mind from my dance classes, this usually takes my off of it. I then tell myself "see, it has passed, there was nothing to worry about". It is like building very slowly on each experience although there are inevitable setbacks now and then.
You need to find the thoughts and tactics that work for you. And you need to believe that you can do this, that this is not out of your control.
Now I shall go and practice what I preach lol
Good luck
