And that is just as it should be.

Your presentation will rarely go
exactly as you envision; there are just too many unknown variables. As
Steve Martin says in his brilliant book, Born Standing Up, someone in the audience might just cough right on your punch line.

But…if you’ve done your homework, if you’ve truly prepared, and if you’re on your toes, you’ll take advantage of priceless unexpected opportunities.

A
great director I worked with used to say in the weeks leading up to the
play, “Do your homework.”  But on the day of the first performance he
would look at us and smile: “Now don’t think about it. Just let yourself
fly.”