『장자 내편 : ４장 인간세 (인간 세상에 관하여)』

To be of service to your parents, despite their position, and to be comfortable with that is the utmost in filial piety. To be of service to your ruler, despite the tasks requested of you and to be comfortable with that is the most complete loyalty. To be of service to your own heart, despite the fact that joy or sorrow have overcome you and realizing that they are part of fate and that neither of them will last for long, is the attainment of virtue.