It's been a few weeks, but I think I found something important that could help treat anxiety.
It's called the Buteyko Breathing Method. I haven't read the whole article at the time I posted this, but it seems absolutely vital in treating anxiety symptoms. It's even covered in the Linden Method manual.
This part of the article should be of interest:
Breathing Exercise to Quell Panic Attacks and Anxiety
Another breathing exercise that can help if you’re experiencing anxiety or panic attacks, or if you feel very stressed and your mind can’t stop racing is the following: Take a small breath into your nose; a small breath out; hold your nose for five seconds in order to hold your breath, and then release to resume breathing. Breathe normally for 10 seconds. Repeat the sequence: Small breath in through your nose; small breath out; hold your breath for five seconds, then let go and breathe normally for 10 seconds. This sequence helps retain and gently accumulate carbon dioxide, leading to calmer breathing and reduces anxiety. In other words, the urge to breathe will decline as you go into a more relaxed state.