You need not lead three cheers for ecological communities, the Great Awakening, or corporate icons, but students tend to take greater interest in material presented by someone genuinely committed to that material. Try not to look or sound bored, even if you have lectured on this topic for years, decades, or twice already today. Use your voice, expressions, body language, and methods of audience interaction to share your passion with your students. Not all of them will follow your lead, but at least some of them will, simply by modeling your obvious interest. And the sheer force of your own enthusiasm will see you through lecturing for the first time or the umpteenth time.