The Keys to any successful system is a strong and grounded set of principles and concepts and it is ability to be adapted to a given set of situations and circumstances.
As a student of systems, including Iyengar and Astanga Yoga; RKC and GS Kettlebells, Bodybuilding, Athletic Training, Westside barbell Powerlifting, Olympic Lifting (newest), Crossfit, Paul Chek, multiple nutrition systems (including Warrior Diet, Zone, South Beach, Mediterranean, etc.) and so much more it is my understanding of the roots principles and concepts of these systems and the ability to take them and apply them to the individual and put them into a progressive program that allows for success physiological, psychological adaptation all while keeping the goal(s) in mind and the present moment. (My opinion based on 14 years of study and practice/experience).
What I often see is people being beholden to a particular system and not truly understanding what it is about the system that makes it tick. The challenge is these often are the people teaching the system not just the people practicing it (i.e. the students). The dissemination of information is critical to the understanding and progression of any system and the people operating within the system.
Therefore it is essential to understand/learn the key principles/concepts of the system and then how to apply them across a large bandwidth keeping in mind that versatility/adaptability is a neccesity because in order to progress we need to understand all the variables present in the moment and keep in mind that a system with strong principles will stand the test of time and the present because it is able to adjust accordingly and still be in a constant state of progression versus digression.
What also must be kept in mind is simple logic and science that up until now has not proven to be anything but truth (absolute I am not sure, but as it stands, truth). For example concepts in physics, geometry, algebra, and even more specific to the world of training and athletics things such as General Adaptation Syndrome, Law of Specificity, F= MxA, and so on.
We operate in a world filled with information, ideas, thoughts, theories, systems and interpretations/perspective/points of view but often we forget there is a foundation, a platform for which any thing constructed is built upon. There is room for adaptability, just look at the human species throughout time and this obvious. But we must not forget the basics principles and concepts in which a given system is built upon and we must learn how to implement with as little as bias as possible, as little ego and attachment as possible and keep in mind that we have to be able to adapt to the given moment with the basic principles in mind/action.