Other than medication and awareness, one of the main things that helped was sensory exercises (aka stimming, sensory diet, sensory integration activities). It's normal to stimulate your own nerves when you're upset--think of a stressed person rubbing their temples, angry cartoon characters pulling their own hair, etc. Those of us who are stressed more often or have sensory issues just need to do a whole lot more

I think most forms of meditation and relaxation techniques fall into this category, but available activities are practically infinite, so you can do other sensory exercises without limiting yourself to established techniques. I think the key factor is that the stimulation is predictable and you are in control of it. (Stimulation that you aren't in control of can be more upsetting.)

Here are some I use a lot:

• Press my hands together in front of my chest as hard as possible for several seconds.
• Stretching, like you would do before exercising (mostly arm stretches for me).
• Pushing against my car steering wheel so that I'm squished against the back of the seat. (Also, pushing my hands against the ceiling, but that's only when stopped at a red light.)
• Listen to music that I've heard a lot before. (It must be the same recording, for the predictability factor. New music, live music, or covers of previously heard music will not work, even if it's music I like.)
• Draw pictures. (Aimless doodling works too.)
• Humming.
• Hand-flapping, leg-bouncing, rocking back and forth, fidgeting of all kinds.
• Deep breaths, so as to cause sensation in my chest area (and nose/throat).
• Sleep with a heavy blanket.

That's nowhere near a complete list.

Sometimes you have an urge to do a particular sensory activity which may not be a good idea (maybe emotional eating, self-injury, something socially unacceptable in your present situation). I've found that substitute activities pretty much never feel as satisfying as the one you had an urge for, but doing a substitute is definitely better than nothing.