All the usual boring stuff. Therapy, painful introspection, diligent exercise and meditation and yoga, regular sleep, good diet. And, having a lot of really awesome, understanding, supportive people in my life has been absolutely essential for me. I'm not brilliant or especially strong, but I've never had a hard time leaning on people when I need to and I have been blessed with lots of people to lean on.
That said, I've never grappled with severe hyperacusis, but when I was dealing with it at all, it was a direct result of being stuck in a state of severely heightened stress and almost no sleep for weeks/months straight. So I believe the adrenaline/H theory.
And, don't get me wrong, it's not a cakewalk. I'm not "fixed". I deal with anxiety daily, sometimes worse than others. If I measured success as "I feel awesome all the time", I'd never get there. But, I have a lot of awesome things in my life and I can enjoy them a lot of the time, so that's good enough to keep me going.