Be strict with yourself, be strict with yourself first; To correct yourself, you must first make your heart upright. "Law-abiding people should be self-disciplined first, and then correct themselves first." This is the wise saying of people of insight in all previous dynasties in China.
Law: constraint. Explanation: to restrain others, we must first restrain ourselves. You should set a good example for others. That's the so-called don't do to others what you don't want them to do to you.
To put it completely: a righteous man should correct himself first, and a legal man should discipline himself first. It means: to make everyone do it well, you must first do it yourself. If you ask others to do it, you must do it first.
To educate others, one must first learn to be a man. The premise of being a good person is to learn self-discipline.