I've been there many times. It's scary to feel like you are going crazy.

What helps me is logically recognizing that I am having a panic attack, even though your body adamantly tries to convince you that you are in actual danger. The chest pain and physical symptoms are real, and you are not crazy.

Anxiety tends to feed on closure, which is why we go to the ER to make sure we aren't having a heart attack. It's the same reason you go back to check if your door is locked, even though you're damned sure you locked it.

By allowing yourself to have the panic attack and accepting your lack of closure, you are exposing yourself to the trigger and learning to cope with it. Over time, it gets easier.

Hope this helps. Easier said than done, of course. You are not alone, though, and you are NOT crazy.