Start Strong, No Excuses, and Ditch the Post-Mortem.
Regardless of your skill level, never begin any presentation or speech with an apology. Don’t warn listeners that you’ve never done this before, or ask for their forgiveness if you stumble. Prepare a strong opening and then practice it. You have about 90 seconds to grab your listeners’ attention, don’t squander it on false modesty.
If, during your presentation, something goes wrong (a pet on the desk, an uncooperative chair, a weak connection), don’t launch into excuses. Stop talking and take a breath. Then communicate that you need a moment to sort out the issue. No handwringing afterward.
Once your presentation is over, don’t immediately dissect your performance. It is still too fresh. Live with it for a few hours and then list 2-4 things you could have done better, and set out how you will put them into practice. Don’t analyze your performance to the point you become a wreck. This will only make you anxious and affect your next presentation. Focus on improvements and then walk away.