I'm going to freak out in a store parking lot
Why do you think you'll freak out in a parking lot?
That there might be a car crash, and nobody will notice it.
Scary things can happen but you should be able to control yourself and stop yourself from making a spectacle of yourself. People will think that you are crazy if you freak out in public.
I don't think I can help it.
If you think you're going to freak out, then I think you should see a professional about it. Living with anxiety is difficult, but a therapist or psychologist is available to help you.