I haven't experienced anywhere near this level of anxiety, but I've definitely had some anxious stretches (mainly early on in my recovery). I actually had a panic attack in the middle of the night that my girlfriend had to talk me through by phone. That had never happened to me before.

On a general level, I would say do anything and everything that helps you calm down, rest, and relax - even if it's just 5 or 10 minutes here and there to start. Think small steps. The main thing is learning (it can take practice - be patient) to get yourself into a state that allows your brain to heal.

A few things that have helped me include keeping the lights off or low, taking a hot bath, lying down on the couch or in bed for 20-30 mins (in comfortable clothes or PJs under a blanket or duvet), meditation, going for a walk outside, listening to some calming music for 15-20 mins, getting some fresh air (even by opening a window), getting some exposure to natural surroundings or green space (again, even through a window), making something simple to eat, minimizing caffeine and sugar intake, talking to a friend or significant other in person or by phone.

Note that one of the threads running through these strategies is keeping stimulation levels low as much as possible.

And patience - recovery can proceed very slowly and take weeks, months or years.