Life is a constant battle between engaging in activities that are tension relieving vs. goal achieving. Self-discipline is the only counterforce to the Expediency Factor--in other words, doing things that are easy or expedient versus things that may appear to be difficult but that are essential and very important. Self-discipline is a Fruit of the Spirit. The simplest definition of discipline is the ability to make yourself do what you're supposed to do when you're supposed to do it--whether you feel like it or not. We could say discipline is when you exert great effort and achieve something that is not natural for you. Remember, the greatest form of discipline is the discipline you impose on yourself.