Reflecting about what you are learning or have learned on some sort of specific schedule is not necessary. Nevertheless, if you are working at learning something new, it is important to constantly upgrade and restate important ideas while making connections between them when you can. All this helps to reorder the learning process constructively as you move forward. The goal is to teach yourself everything about your subject, constantly reassessing important points and issues, ordering and reordering your subject until you begin to feel comfortable with it. Then you will still reflect on it , but perhaps at less frequent intervals. But is the goal really to progress to being comfortable? Is that why we reflect?
Perhaps the strongest or most powerful reflections come to you spontaneously. You have thought about the subject with some intensity and thought that you had put it out of your mind. Just at such times there comes a strong impression that two ideas or facets of your subject are important to consider together in a relationship that seems clear even if you cannot quite say what it is. At that point conscious reflection on the connection can yield results. Often you will see multiple possibilities. Write them down. Add commentary on each independent possibility. Then put away those notes or tack them up on a board, but don’t let them get lost. This may be where you want to begin further reflection later.
Often powerful reflections come while you do not yet know much about your subject. You are still too naive to know that some connections may not be possible. But, is that really true? Seasoned teachers will often say that they value teaching beginning classes in their subject because students who do not yet know much are capable of interesting insights. Later, they will know too much and will never again quite think about the field in the same way. Knowing too much may mean they have accepted certain rules and dogma associated with the field as basic axioms, which are taken to be true without proof. But if you are prepared to challenge even the basic truths of the field, careful attention to what beginning students think may be important. They may challenge certain connections before they know that they are cemented as axioms. This gives you the chance to reexamine whether such “truths” should really be axioms–a challenge far less often taken on by long practiced scholars in the field. Are there conditions, you may ask, when these “truths” may not actually be true?
In many fields of knowledge fundamental new discoveries are made only when you are willing to challenge the most basic ideas. You can know too much. After that you may believe there is nothing more to learn. Reflection on basic ideas dims and soon you may become entirely too comfortable with the well-worn ideas of the field to ever again reflect on their validity.