Hi dberry. As a matter of fact, I developed similar symptoms just a couple of years ago. The breathing techniques/mental control aspect is important.
So too, though, for serious asthma attacks, are medication ... and medical attention in the worst cases.
There are actually a number of different medical approaches to treating and preventing asthma attacks, as you know. My approach has been to do my best to stockpile preventive inhalers (i.e. Flovent) as well as rescue inhalers and rotate through them before they expire.
For any medical condition that requires medication or medical supplies, stockpiling those items to the best of your ability is advisable. Talk with your doctor about it. Many doctors today are perfectly onboard with emergency planning and preparedness. If you doctor has reservations about helping you with your needs, I'd suggest finding another doctor.
Here is the Mayo Clinic Asthma web info
Disclaimer: I am not a medical professional and any advice offered here is to be received as generally non-specific and of limited value.
Please note, dberry, that I do have a very qualified medical practitioner on my Safecastle Board of Advisors. If you'd like, I can invite you to forward your questions on to him for his consideration and a personal response. Please email them to me here: firstname.lastname@example.org