I've had panic attacks and anxiety since college. DX GAD and borderline OCD. Came out of the blue. First night it happened, literally thought I was going to die. My body was telling me that. Ended up in the ER twice with them over the years - once presenting symptoms for heart testing, i.e. EKGs, heart monitors; another presenting symptoms that made them give me an CAT scan. You feel like an idiot when the doc comes in and says "oh, it's just another panic attack." You don't believe them, you second guess them. You second guess yourself and what you felt.
I've had to leave places because of them, including Disney on two occasions. They've happened on good days when things were going great - a no-stress day at a previous job, a fun time out at the beach, at Christmas, in the middle of Christmas shopping at Walmart one day - any and every situation you could imagine, I've had. I've been on meds before - clonazepam and zoloft, xanax, and valium. I weaned myself off all of them. They did nothing but made it worse w/ worse side effects. I've gone to psychologists about it - they sucked. I've gone to acupuncture, reiki, bodytalk, chiropractor, spiritual healings, naturopath, done diet cleansings, etc. - you name it, I've done it.
I learned that a lot of it is mind control, taking control of one's self, one's surroundings, breath techniques, centering oneself, etc. - all important.