You know when you're about to say something and suddenly your mind goes completely blank? (Hours later, in a bittersweet stroke of genius, you'll think of the perfect words.) We've all been there: Brain freeze is a natural result of the body's fight-or-flight response to anxiety-inducing situations. The sympathetic nervous system triggers a hormonal cascade in the brain that temporarily suspends your ability to organize your thoughts, leaving you flustered. For advice on performing under pressure, whether you're in a private conversation or a roomful of people, we went to the pros—five folks who make a living thinking on their feet (including a law professor, an improv coach, and a TV show host). Here, their smooth-talking secrets.