I used to get them, went to the doctor and he said - imagine stress is like a glass of water, half full then you go on holiday and reduce the level, then the level increases. When you miss a holiday or two, the glass becomes nearly full. Then one little thing, one single drop of water causes the glass to overflow, and that's a panic attack.
I mentioned Monika Frank and her website Excel at Life in a previous post:-
HERE... I just looked, and she's got a webpage on panic attacks called
"Panic Assistance" There's a downloadable tape which I have used many times. In fact, I uploaded it to my Google Music, and it says I've listened to it 67 times! The tape is very good. If you load it up to Google Music or put it on your Google Drive you can play it on your mobile, out loud if you are by yourself, through headphones if you want a bit of privacy...