Mom says never apologize for kitchen secrets. Does this apply to speaking? Absolutely. Are you nervous? The audience may not even notice.
Keep it to yourself. A graphic element or content missing? Don’t tell. Only you know the presentation. They will not even notice. Disaster strikes? Power outage? AC breakdown? Acknowledge the elephant in the room. Let the audience know you’ve done what you can to alleviate problem. Should you need help, enlist the audience to create a positive group dynamic. Then, proceed with the speech. — Sharing your secrets may diminish your credibility and solidify that you feel unprepared.