Literally, there are mainly the following different opinions. The first is Zhu's views on the four books. If you keep learning from it, you will be familiar with it, and the center likes to say that it is impossible to enter it. The second is the explanation in some Chinese textbooks now. Isn't it fun to study and review often? The third is Yang Bojun's explanation in the annotation of The Analects of Confucius,' Isn't it happy to explain, learn and then practice at a certain time? In the eyes of some scholars, they think it is unpleasant to review after learning knowledge or skills for a certain period of time.
For these explanations, the last emphasis is on the relationship between learning and learning. Learning is only a cognitive process, and learning is a consolidation process. If you want to gain more knowledge, you must unify learning with learning.