Announcing our sin

Our lunch discussion today
Me: I don't mean to brag, but I make a really good sauteed spinach.
Sarah: You just bragged. Saying "I don't mean to brag" before bragging is still bragging.
Me: You're right. In fact it's worse than bragging, because it's like announcing that I'm about to sin and then doing it. Premeditated sin.
Sarah: It's like when you say, "No offense, but..." and then say something offensive.  Remember you taught us that just saying "no offense" doesn't cancel the offensive thing you say right after it.
Me: Right.
Noah: It's also like saying, "Not to complain, but...".  You know the next thing out of the person's mouth is going to be a complaint.