Usually there is some incident in our lives that causes us mental strain or anguish. It could be an accident or the death of a loved one.
Later in life, something in our environment will trigger the memory of that incident (but it does so below our conscious level). Your mind wants to protect you from experiencing that same mental anguish and so you get the feeling that you have to run, or hide, or that you can't do something.
However, the thing that triggered this "panic attack" could be something really harmless, yet your body feels the "fight or flight." And because it's all below your consciousness you don't understand why you're panicking. You just know you're afraid or on edge.
There is something you can do. www.dianetics.org. Just buy the book, read it, and use it. It has helped one person I know get over his panic attacks!
It's just a book. So I would think it's worth a try! If you don't want to get the book you can get the DVD :)
Hope that helps! It's much better than medication! And cheaper too!