what 20 words will assure your patient about safety of his life in your hands and remove his or her anxiety and tension about surgery to be performed upon him or her.
I doubt there is a magic set of 20 words. And words alone are not enough.
My pre-op talk is tailored to each patient (based on their level of understanding and anxiety levels) and I think the manner is as important as the words themselves. Being calm, reassuring, and listening to their concerns are all as important as the content of what you say.