There are a few things I do; first things first, find yourself a safe spot. For me, it's my closet. Get a anxiety kit; your favorite snack, something to smell (like chapstick or perfume), a small toy (cards?), a texture you enjoy (rubber ball? silk?), something to listen to (a toy that makes noise or something that plays music), and something that means a lot to you. Keep it in your safe spot. There are two breathing techniques that work best for me; breathing from your diaphram (move your stomache when you breathe deeply) and the Hawaiian technique (deep breath and then force the breath out like you're trying to poison someone via bad breath, not like blowing out candles, keep your mouth wide instead of fish lips.) Use your anxiety box as you wish. Learn some yoga that you can do in your safety spot, like Cobra or Sun Salutation. Listen to songs you listened to when you were young that don't have any sad memories attached to them. Fill up a 2liter bottle with water and lots of glitter and shake it up and watch it as it settles (or use a snow globe.) Keep your mind focused on something that isn't what's stressing you out. Excercise if you can. Drink some tea that tastes good to you. Spin until you feel dizzy, stop, then spin more until you feel better (But don't get hurt!!!) And if it's really, really bad, you can either take a shower or a bath; a bath if you need comfort and a shower if you need to have everything washed away.