When things don't make sense, I try to look at the "opposite" and laugh? I assume your sudden anxiety pretty much passed/wore down after awhile. As long as you don't concentrate on it, it can't do anything else. I'd do like Brookester suggests and let some out somehow. I'd make a list of ways I could do that, try to distract my mind with a task in that way. If you can't scream for "real" because you're stuck inside with others and it's night, etc. how could you "express" a scream silently. I'd find a picture to express it like Edvard Munch's http://www.ibiblio.org/wm/paint/auth/munch/ famous painting, The Cry. Maybe start a collage or collection of pictures/text that helped me when I was feeling as you were, etc.