I get it too! Terrible, terrible feeling. Think I am going crazy but guess what, when you accept it and let it come, it goes away. It takes time and patience and I still get it at times but it does go away if you are confident it will and can accept it (dont try to forget it as that can make it worse - as already said)

the more you focus on it, the more it comes... As said, vicious circle.

And yes I know it, I had it off and on for 5 1/2 years and sometimes it was with me for months at a time, almost always. It runs you down and feel terrible, but the only thing that ever helped it was to stop thinking about it by a combination of distraction, positive thinking and exercise.

I still get them but they get less and less each time as I am learning to pay less attention to it (as scary as it is).

Cheers
Paul