I don't intend to explain the Four Great Realms of Heart, but the content of the education of heart. We have four responsibilities centered on love. Because of irresponsible love there is so much confusion.
People love without responsibility.
Because there are Four Great Realms of Heart, then there are four areas of responsibility. Even children, whom we normally think are not responsible, have their own realm of responsibility. As children begin to walk, their learning responsibility should also begin. Because the mother takes care of children, the husband does not know about this early development of responsibility so much. If children are taught responsibility at 3 years old, they will be responsible till 100.