Other tips (I suffer from anxiety badly and I am on a course now to help resolve it).
Breathing in to a count of 4 and out to a count of 6. What most people don't appreciate is that its the out breath that calms you down and the in breath does the opposite. So, a longer outbreath than an in breath will help. Also, focus on the outbreath and feel it in the stomach (where we feel our most grounded and secure). You will end up relaxed if you do this. It may take time though. I use it when I wake up in the night.
Progressive muscle relaxation. This is alternately clenching and relaxing muscles in your body. This leaves your body feeling relaxed. If your body feels relaxed the mind follows. You can find guides on how to do this on Insight Time or the Glasgow IAPT Website has a good one.
Mindfulness Meditation (that old chestnut that everyone mentions). This really works but it needs time and consistency. A daily body scan for 8 weeks will have a huge impact on your body, mind and anxiety. I know as I did an 8 week MBSR course and didn't suffer a migraine the whole time. Sadly I've gone off the wagon (meditation wise), so I am back in Anxiety Hell. Mindfulness meditation has helped me loads though and I'd not be here now without it. I would recommend Tara Brach's free mindfulness course (I'm not affiliated) or reading and following John Kabat-Zin's Full Catastrophe Living which the 8 week course I did was based on.
Sleep - easier said than done this one, but if you're not getting enough of it, you will suffer during the day and be more vulnerable. The key appears to be getting up a the same time and going to sleep at the same time no matter how you feel. There's loads I could write on sleep hygiene, but I assume you know all that. Aim for 7-9 hours a day depending on your age.
Eat well. Don't eat too much or too little. Eat regularly and mindfully. Stay away from foods that make you emotional (like chocolate and cheese do for me).
Avoid alcohol, illegal drugs & caffeine
Exercise 20 minutes a day
Source: NHS handout "TIP Skills - Changing your body chemistry" and a life of suffering depression, stress and anxiety for the last 25 years. I'm still here though and I even smile sometimes. ... just not right now as my car was involved in an accident last night and I'm waiting for confirmation that its a write off...