i get it.i use to have them all the time.you should check out this guy hes helpful.i dident buy anything but i watched some of his promotional Videos he helped me enough link
Find a set of sounds and Bilder that are very soothing to Du (for me its the opening of gwen stephani's what Du waitong for) then focus on them. Weiter find a feel that Du like, like a type of fabric and carry it around with you, then find a smell that calms Du down like a candle and carry a mini with Du ( I reccomend the miniatures Von yankee candle company). Von surrounding yourself with familiar sensations you'll calm down.
If that doesn't work try and stare at people. I know it sounds creepy but Von focusing on others rather than yourself it can relieve stress.
Mark your Favorit passages in a book and keep it with Du so that Du can read it when need.
Another weird thing, try to make Musik with your breathing like short short long, long short long, long long short.
