Some measures of success in life require the development of some of the many virtues. Discipline or self-discipline and thinking are some of these virtues.
Self-discipline is the ability to do things that ought to be done. Focus on what ought to be done may be an important element of achieving success. Think of the focus by a great athlete like Wayne Gretzky or the focus of the Wright brothers who created the first powered aircraft in 1903.
Critical thinking may be an important element of reaching a goal. Critical thinking is an important component of most professions. It is a way of deciding whether a claim or opinion is true or false or sometimes true or partly true.
Being a successful student requires not only a good memory but an ability to think. “What the Harvard student needed above all was the chance to learn to think for himself” see Brave Companions by David McCulloch.
In law school I remember being asked “Appleby, what do you think” about a judge’s decision. It took me some time to realize the professor was not looking for a specific answer but wanted me to think about the issue or problem.
Recognizing an issue or problem and the ability to state it is the first stage in thinking about an issue.
My law school dean used to say the a student will get a passing mark if she can state the issue or problem. The dean added that an opinion on how to solve the issue will result in a higher mark and an ability to state the arguments both pro and con will result in a still higher mark. The best students can do all of this.
Some students are bright enough that they can think and excel at exams without having to develop some self discipline. A less talented student may have to develop a discipline that will be of great value in later life.