This TED presentation by Daniel Levitin will help you prepare in advance of a stressful situation so that you can maintain calmness when that actually happens. The presentation is humorous, short, and very useful to many. I liked that way Mr. Levitin explains his methods and the reasons why they will be useful. Given that everyone will face some stressful situation at some point in her/his life, the need to be prepared to face those well cannot be over emphasized.
Use the link below to watch this valuable presentation.