...Always prepare, and always be prepared to adapt to the moment.
There's nothing worse than having had the opportunity to speak and then to have missed making the right point.
I was tossing and turning last night because I kept rehearsing the speech I wish I would have made at a city council meeting last week. I was too attached to my pre-written talk. I was afraid to veer off the plan and be impromptu, but wished I had dumped my speech, and instead referenced all those who had so eloquently testified before my turn, and made kind of a closing argument. That would have been effective!
Prepare? Yes, absolutely do! But be prepared to switch gears and capitalize on the changes in the room.
That is the key to making a powerful verbal impact.
And the way to avoid spending sleepless nights re-rolling the tape on what you wish you had said.
Another time I prepared for a music camp session for elementary age kids. What I didn't know was their temperment, age or abilities. I practically threw out the order of activities, but was very glad to have brought pre-planned tools, instruments and videos in for the class.
When speaking and teaching, always prepare, and be prepared to adapt to the moment.