..that you've learned so far in your journey as a presenter that you wish you'd understood from the beginning!
Example; When I got tricky questions in a meeting or in a presentation, I felt like I had to answer them directly on the spot. This sometimes put me in a "bullshitting position" where I just made stuff up. I later understood that It's okay to not hold all the answers, it's okay to say "You know what, that's a REALLY good question, let me look it up and get back to you on that".