I've had periods where I suffer up to thirty panic attacks in a day. What has helped me break out of those anxiety cycles is medication (Citalopram), but I can only tolerate medication in the short term. There is some literature that suggests people on the spectrum are more sensitive to psychiatric medication. Long term coping mechanisms that I use involve reducing stimulation (ear plugs in public spaces, giving myself plenty of alone time, etc.). I don't know what your situation is, obviously, but sometimes, regardless of whatever stressful circumstances emerge in my life, controlling the amount of external stimulation that I receive can reduce anxiety. Otherwise, try to take deep breaths and talk to yourself. Sylvia Boorstein, a teacher and writer on Buddhism, has written that she speaks to herself in soothing tones when she is anxious or stressed saying things such as, "I know you're stressed, sweetie, but this will pass." It is kind of silly, but sometimes you can try and talk yourself out of a panic episode or at least imagine that you are supporting yourself through it from an external perspective. I hope this helps! Good luck and feel better!