Discipline is the cornerstone of the Cornerstones. Important in its own right, it is an essential component to the effectiveness of my other Cornerstones. I believe it is the foundation of success. For me, nearly everything comes back to proper discipline.
Developing and establishing your own personal discipline is tricky, however, because to do so requires discipline. It probably will be difficult at first (which should be expected) but if you can commit to stick with developing a habit of discipline, it will be the habit that defines all your other habits.
I discovered my own principle of discipline while studying martial arts. Without consciously knowing it, I began to apply the same type of discipline to other life pursuits. The benefits surprised me and when I realized what I had unconsciously applied, I quickly adopted Discipline as the key to achievement. But for it to work, you must be unwavering. Remember when I mentioned not going all the way to the bottom of the barrel before getting a grip? Some call it willpower, but even willpower needs discipline. That's my sense of discipline. For instance, I woke up one day and decided to quit smoking. No aids, no delays, no wishy-washy attempts - just purpose. I took the same exact approach to drinking. I just stopped completely - no gradual degrees of drinking less. Singular purpose and commitment. That's the habit of Discipline.
Discipline is a habit like any other. Ingrained, it can be a powerful determinant of your other habits. Unpracticed or neglected, it's effectiveness wanes. To help maintain mine, my mantra is, "No Excuses...ever." Devise an action plan and follow it until the goal is achieved. You must want to achieve the goal. You must remind yourself you have a plan to follow. No excuses. Singular purpose. Discipline.