Hi Sara:
Eager...what a great adjective to describe what all teachers would hope to encounter in all their classes all the time! I love it!
Probably not realistic, but your point is true - prepared teachers convey confidence, conduct classes seamlessless with a flow, even with questions or interruptions.
However, the teacher does have control over their enthusiasm, enjoyment and mastery of the topic, and creating a learning environment that students look forward to - interesting, exciting, beneficial - therefore, we can inspire and motivate, and I think these are worthwhile challenges to aspire to.
Regards, Barry