"Sound familiar? More beer? Other substances? Yoga? Deep breathing? Tantric tuning?"
I can't answer to the putative benefits of beer, other substances, or yoga. But as to deep breathing, I have one word: DON'T!
At Banjo Camp North a couple years ago, Peggy Seeger was addressing the subject of nervousness, and she said something like, "That's the last thing you want to do."
But she went on: "EX-hale, all the way down to your crotch. Let your shoulders fall. This is very relaxing. Then just let normal breathing take over; DON'T take a big inhalation.
"When you take a deep breath, you fill up your capacity and you raise your shoulders, and you tense up. Now, with your lungs full, and tense, you can't get a breath, and it makes you panicky and you tend to fall apart. EX-haling does the opposite for you."
I probably haven't said it as well as she did, but that's her message in essence. And I can tell you from personal experience that it works.