Don’t apologize before your set. Let them decide if it’s bad.

An apology tells the room what to expect before they have seen anything. Saying you are nervous or that this is new sets an audience up to look for flaws, and they will find them, because you asked them to. Confidence here is not a claim about quality, it is a decision not to pre-judge on their behalf. They are perfectly able to make up their own minds.

Walk on and start with the material rather than a disclaimer. If something fails, let it fail without narrating it. Save the explanation for afterwards, with somebody whose opinion you actually want.