The worst lies are the ones we tell ourselves. Quite clearly if we vow to never leave a marrige, that is a lie we tell ourselves. It's like we tell ourselves it's OK to run out onto the Freeway! We believe it, but when we actually run out into the Freeway, we are quickly faced with the truth and are killed. Do we really want to believe the lies we tell ourselves? I think it would be a lot more practical to say vows that are truthful and that you can actually stick to - like we choose to be together and this lasts as long as it lasts - none of this death do you part stuff.