The most important thing in the programming world is to keep learning and practicing.

We change our behavior when the pain of staying the same becomes greater than the pain of changing. Consequences give us the pain that motivates us to change.

里氏替换原则是面向对象编程中的一个基本概念，它指出子类的对象应该能够替换超类的对象而不影响程序的正确性。