My kids will never behave that way...right?

So I have been in Salt Lake City for a training since early Monday morning and I flew back this afternoon. On my flight from Denver to Des Moines I was seated behind a family of four. There was a work-out looking man (Dad), an irritated looking woman (Mom) with a lot of make-up and very youthful clothing (that is my polite way of saying she was dressed like an 18 year old Girls Gone Wild Wannabe), and two girls approximately 6 and 10. So there was a row of three seats in which the Dad sat on the aisle and the two girls sat in the other two seats and Mom (partied-too-hard-in-her-early-days Barbie) sat across the aisle from the rest of the family with headphones on looking annoyed. From the moment they got on the flight the two girls were fighting, hitting, yelling, whining, and generally annoying the majority of the plane's other occupants. This pretty much continued for the duration of the flight as Dad ineffectively tried to get them to stop and Mom offered the occasional "You are in so much trouble." As my co-worker and I observed this (she has no children yet) she leaned over to me and said 'Are you sure you're ready for that?" I replied with a phrase that has become a staple in my recent conversations: "My kids won't behave that way."
I say this phrase often as I sit at restaurants, shop at Target, and wander through the mall. I am beginning to wonder if this is a self-soothing mantra that all first-time pregnant people repeat to themselves...