Do NOT do breathing exercises to curb anxiety, because that will just reinforce the pathways in your brain and your anxiety will keep recurring.
If you're noticing you're mind is dwelling on anxiety-inducing thoughts you need to refocus on your current task.
Just keep doing that whenever symptoms popup.
The symptoms will popup less and less frequently, and you'll have developed such strong coping mechanisms that you automatically handle the issue.
This is approach is called "cognitive behavioral therapy" or CBT, and is an evidence-based approach used widely. You can consult a therapist and get taught CBT skills by a professional. (That's what I did)
In addition to learning CBT techniques, and get regular exercise and enough sleep. I recommend you cut out all caffeine until you have developed strong CBT skills. Of course, rule out any underlying medical issues and work on any medical conditions (obesity, bad posture).
Once you're comfortable you have anxiety under control you can slowly re-introduce caffeine.
Source: I used to have severe and debilitating chronic hyperventilation and anxiety, but sought help from a CBT therapist a few years ago. Now when I am living my life and notice I've started hyperventilating (or dwelling on an anxious thought), I can immediately stop it by refocusing. It's changed my life and I highly recommend learning the CBT techniques.
I highly recommend a few sessions with a CBT therapist. If you're not in a position to do that you might be able to learn about CBT techniques from elsewhere, such as YouTube.
I tried it for years with multiple psychologists and had no progress. Eventually, I found a great psychologist who helped me with a blend of IFS ("internal family systems") and mindfulness to help me not constantly unknowingly suppress feeling and allow me to be present and process emotions.
There's lots of approaches out there, so if anyone's not making progress, try out some of the others!
This sounds speculative. Is there actually empirical evidence that this is the case, or at the very least that intentional, focused breathing exercises interfere with handling anxiety?
This is also why I recommend the book “the healing power of breath” its one of the best books I found on the topic without confusing you with all kinds of techniques and so on.
Basically in the beginning you practice 20 minutes a day in rest, so your bodymind starts to adapt to it, and it may overcome the causality that leads to anxiety.
Usually I'm relaxed in the morning, then go to work, enter a state of flow / complete focus, then at the end of the day I'm anxious (this becomes worse when I enter the supermarket for my evening groceries, even as I continue to think about work) and my breath is messed up (short, shallow breathing).
How would your method help here? For me it seems there is a contradiction, or not? Could you explain?
With that said, the CBT advice would be to recognize that thinking about your work in the evenings is causing you anxiety, so to stop getting anxiety you should refocus on the task at hand (shopping for groceries) and stop thinking about work. It's OK to let your mind wander while you shop for groceries, but CBT is about catching yourself when your mind drifts back to a topic which causes you anxiety (your work), and then using the task at hand (shopping for groceries) as a tool to basically distract yourself.
How you can make thinking about work cause you less stress is a different question. My personal advice is to try exercising after work, you'll feel very relaxed after. But if you're finding you're still stressed after work, my suggestion would be to seriously considering stopping your thoughts about work after hours (again, by catching that you're thinking about work and refocusing). Chronic stress kills.