Society has rules, and through those rules gives way to personal codes and ethics. A ruler might vow to always watch over his subjects, and at the same time, a commoner may vow to always obey the laws that his given sovereign lays down before him; but a vow is only as good as the person who makes it.
What good is a noble who's very willpower can call forth gusts of wind stronger than any tornado, or tongues of flame hotter than any natural fire, if they don't have the force of will to keep their word and grasp their ideals? It is that question that separates the commoners from the nobles, the magic users from the mundane.
Louise de la Vallière, youngest daughter of Karin the Heavy-Wind, and perhaps the one child that took the most after her mother…viewed those words as the pure, untainted truth. Her mother referred to them as the 'Rule of Steel', and it had, subsequently, been her first lesson in magic. A sort of mental exercise meant to build character, but also hewn the mind to be unshaken by all but the most extreme of cases, and not even those.
Upon her first lesson, Karin had told her daughter that she expected the girl to hold herself to the same ideals that she did: to the sovereign, the laws that made up their land, and to the subsequent rights of all nobility and their divine mandate to rule over the common masses. Louise had taken her mother's words to heart, and in some small parts of her, continues to do so to this day.
However, her first failure in magic led her mother to decide that her daughter's efforts were without conviction; and so she and Louise revised, and revised…and revised. Failure became the flavor of the day, then the week, then month, then year, until Louise's Rule of Steel wasn't so much about keeping loyalty to her sovereign and maintaining the rights of nobility, but instead persevering in the face of persecution.
She would never give up, no matter how many times she failed. She would never stray from her goals, even when her mother looked upon her with half-lidded eyes, even when it would be easy to do otherwise. She would recast her spells, even when they would always inevitably fail. Quit was not a word that she understood, and she would continue to venture forth: in omened-weather, against daily trials, and not even the founder himself could stop her.
Unfortunately, when you don't check your path from time to time, it's easy to get lost.
AN: My interpretative views on the whole 'Rule of Steel' issue prevalent within Karin the Heavy-Wind, and Louise de la Vallière as a result.
Also why I love her character.