Buttercupistiny's "How to calm the fuck down using breathing" exercise

Reposted from IRC:

[7:12pm] <Buttercupistiny> Bear with me here, because I was taught this when I 
was nine or so, and it's just second nature. So. In theory you could do this 
first bit sitting up, but it's easier to monitor if you're lying flat, in my 
opinion.
[7:12pm] <Buttercupistiny> 1. Note the level of tension you're feeling. Then 
put a hand on your abdomen, right below your rib cage.
[7:13pm] <Buttercupistiny> 2. Inhale slowly and deeply through your nose into 
the "bottom" of your lungs-- in other words, send the air as low down as you 
can. If you're breathing from your abdomen, your hand should actually rise. 
Your chest should move only slightly while your abdomen expands.
[7:13pm] <Buttercupistiny> 3. When you've taken in a full breath (count of 4), 
pause for a moment (count of five), and then exhale slowly (count of six) 
through your nose or mouth, whichever you prefer. Be sure to exhale fully. As 
you exhale, allow your whole body to just let go
[7:14pm] <Buttercupistiny> Do ten slow, full abdominal breaths. Try to keep 
your breathing smooth and regular, without gulping in a big breath or letting 
your breath out all at once. Remember to pause briefly at the end of each 
inhalation. Count to ten, progressing with each exhalation.
[7:14pm] <Buttercupistiny> Slow inhale... Pause... Slow exhale (count one) Slow 
inhale... Pause... Slow exhale (count two) and so on up to ten. If you start to 
feel light-headed while practicing, stop for thirty seconds and start up again.
[7:14pm] <Buttercupistiny> And there you have it.