Maybe I live in a delusional bubble of my own creation, but I have never suffered from stagefright. Not during my very first performance in Kindergarten, nor doing a live radio broadcast, not on large stages in front of thousands. Not even after months or years off the stage.
I can, however, relate to the sensation of being a fraud who's in constant danger of being found out. That's pretty normal, I think, and has no relationship to one's talent, accomplishments or even self-confidence.
You know your own limitations intimately and wonder how many in the audience can spot them.
Ironically, if you
don't feel this way then you probably
are a fraud with an inflated sense of your own brilliance.
My own self-medication, which I employ only in extreme situations, is coffee. Whether it's going into the studio to lay down a part for someone else or performing live, caffeine speeds up my brain and my fingers to the point where I find myself looking down at my own hands and being surprised by what they're doing. This only works because I am normally not a big caffeine consumer, so all it takes is one Starbucks Iced Coffee to wind me up.
A less-dangerous technique is simply warming up before a gig. I sit down at the keyboard with headphones and start doing finger exercises, scales and a self-jam around some simple chord progression. It takes a good half-hour for the effect to kick in, but when it does it's even more effective than a double-espresso.