Diaphragm breathing. When I feel the anxiety coming on I start breathing slow and deep into my belly. It brings you back to the present moment where you can almost laugh at yourself for getting worked up over nothing. When you realise you have drifted off again just bring yourself back to the breath and relax as much as possible.
A an Indian yoga teacher, who is a doctor and has more degrees than I’ve had hot dinners once told me that if I forget everything he tells me to at least remember to breath deep into the diaphragm, it’s that important.
In the book “The Way Of The Superior Man” the author recommends you breath into your belly any time when you’re “under threat” e.g someone had just insulted you and you feel anger beginning to arise.
It’s all about bringing you back to the present moment. Anxiety is worry about the future and can’t exist in the present moment.
Yogis, western spiritual teachers, military personnel in high threat environments, jedis - all use slow deep breathing.
I know this might seem a little wishy washy but I hope you can get something out of it.