Being disciplined with your fitness can change your life. To me, its to obey rules and/or stick to your plan being disciplined in fitness means to me means (following a training plan, eating well, recovery).  Discipline allows you to test and measure and pivot (if you follow a plan you can find out what works well for you and what doesn’t). People are never disciplined to follow something for the required time. This can relate to all aspects of life.