Why longer exhales?
A long exhale nudges the parasympathetic side of the nervous system and slows heart rate. It's the most reliable lever you have that doesn't require anything except your own lungs.
It didn't work when I was really angry. Why?
Because you tried it for the first time while really angry. That's like practising a fire drill during a fire. Do the calm reps for two weeks, then try again.
Is this a treatment for anxiety or panic attacks?
No. Breathing techniques can be part of a plan built with a clinician, but if panic or anxiety is regularly disrupting your life, start with a professional rather than a protocol.
Can I do this discreetly in a meeting?
The double inhale is noticeable; the 4-in/8-out is not. Nose breathing with a long exhale works fine with a straight face.