Feedback. Some days I would give 5 presentations and after every presentation I would hand out student comment cards. Every year there would be thousands of comments on my presentations.
Most were positive. They were fun to read and share. Some were negative. Some were funny – some were funny good; some were funny bad.
One comment from a student I will always remember said only “I would rather lick a toilet seat than listen to you speak again.” I put that in a frame on my offfice wall to remind me not everyone wants to hear me speak. My boss ultimately made me take it down.