You will “fall on your sword” when you take personal responsibility for an error or other lapse. Plutarch so described Brutus’ suicide when he took responsibility for his part in the assassination of Julius Cesar.

 However, if you do decide to fall on your sword, you should be sure that it is a sword you are prepared to die on… for it will be accomplished in front of your peers in court, and become a matter of public record as a part of the court’s written record of the case.