No doubt, self-discipline is one of the most important life-improvement skills or tools that everyone should have. But there are, of course, plenty of other almost equally essential life-upgrading skills that everyone should have, such as friendliness skills, time and money management skills, survival skills, professional-service skills, communication skills, and more.
Take a moment to review the last sentence so you may realize the sense in which it is to be understood for an accurate application of it to reasoning. Here comes the guiding question: Do you know what all the above noted skills have in common?
If self-discipline is your answer to the common-denominator question, it follows that your answer is correct! You need to have the discipline to be able to acquire an assortment of life-upgrading skills. The possession of specific skills is important for use to succeed at work, at school, at home, or anywhere else.