Self-discipline allows you to be aware when something hurts you. The result is that you purposely avoid things that give you a momentary pleasure but prevent you from having a healthy lifestyle. With self-discipline, you try to use only what I will contribute to your health and ignore everything that harms you.
By the time you have self-discipline, half of your goal is already achieved. The top of self-discipline is when you can make a conscious choice, which generates a vibration pattern that ensures you follow it until you get what you want. Self-discipline is considered one of several resources used for personal development. Although not miraculous, it is able to solve important problems faster and more quickly.