I've always admired people who are over-prepared. In college, I had a classmate named Norman Meyrowitz. One day he was giving a presentation on an overhead projector" and the bulb subsequently went out. The class thought the presentation was over. "It's okay," Norm announced... and he went to his backpack and grabbed an extra bulb he brought with him.

Chapter 46: All You Have Is What You Bring With You, p. 160 - The Last Lecture (2008)