The core of this sentence is "learning from time to time". "Learning" here refers to learning knowledge and skills, and "harmony" is a conjunction, indicating that the next content is a further explanation of the previous content. "Time" means always and often, which means that learners should always review what they have learned. "Learning" refers to practice, practice and memory. Therefore, this sentence means that after learning, we should often review and practice what we have learned in order to achieve better learning results.

This sentence of Confucius expressed his emphasis on learning and practice. He believes that only through continuous learning and repeated practice can we truly master knowledge and improve our ability and quality. At the same time, he also emphasized the happiness of learning, which comes from mastering and applying knowledge and communicating and sharing with others.

In addition, this sentence also reflects Confucius' learning view and educational thought. He believes that education is not only to impart knowledge, but also to cultivate students' thinking ability and innovation ability. He advocates the use of heuristic teaching methods to guide students to actively think, find and solve problems, so as to cultivate students' ability of independent thinking and independent learning. At the same time, he also stressed that education should focus on all-round development and the all-round improvement of students' moral, intellectual and physical qualities.

In a word, this sentence is a classic expression of Confucius' educational thought, emphasizing the importance of learning, acting and thinking, as well as the thought of all-round development of education.