I have a big presentation to give this morning, in front of executives from my company and a committee of the company board. My stomach is churning. It's not stage fright: I'm very comfortable in front of people. I switch "on," like flicking a switch. It's more fear that I'll ramble on during a particular PowerPoint slide, or that someone will ask a question and I'll give an inarticulate response. In other words, it's the unrehearsed stuff that freaks me out. In most situations I wouldn't care - but it's been a long time since I've done anything like this, and this isn't the group to mess up in front of. An improv crowd is more forgiving; the context says "we're trying up here, but we don't promise perfection." I like situations where you get points just for trying. Or better yet, situations with no points at all.
(Growing up, when I was in school plays, my nerves always manifested themselves as an inability to stop yawning. I'd be backstage, moments before curtain, yawning away. Again, I don't think it was stage fright - in fact, I used to say I felt more comfortable on stage than anywhere else. It was fear of forgetting my lines...of messing up. I'm only now realizing that performance is about more than rehearsed perfection... it's about connecting with your audience, being in the moment, thinking on your feet. And then it's about moving on to the next one: new night, new crowd, new possibilities.)