Luckily, I've only ever been on "stage" back in the mists of time in the school nativity play, where I might have been a shepherd. I think "shepherd" is the role little boys get placed in when they're obviously not star material.
I've not had to do much talking to groups, let alone audiences, but enough to know that I'm not good at it. I tend to clam up and have a severe attack of stage fright with pretty much everything getting thrown out the window: memory, speech capability and heart rate. It's a thoroughly unpleasant experience not sought after!
However, I know that many people overcome this fear, and I'd love to manage to do that myself. Mikael Cho's wriiten about his experiences and how he tried (and succeeded) in fixing his own stage fright. There is hope if you try: small steps first I think with very good preparation.