One of the worst ones I've ever had was when I was a freshman in college, and I washed down four Vivarin with a raspberry mocha. One big whopping panic attack coming right up. So I'll have to get out for awhile. I'll sit on the patio or go for a walk until I calm down. It can take most of the night for that to happen though, which is why I'm not getting any sleep lately.
Stress can bring it on too.
Finals, work, fights with the family or whoever the man is this month. Yeah, I tried it. It never really helped though. We're talking instant F here. All the same, I think it would be beneficial if we started you on a program involving some relaxing techniques.