原: 唐書, 房玄齡傳; 觀政要, 君道; 資治通鑑, 等等

創業守成 (창업수성,chuàngyè shǒuchéng,そうぎょう－しゅせい) start [of] work, maintain or protect / act of
Short form of 易創業難守成, which means the start of a work is easy, but maintaining it is difficult.

During a chaotic time, near the end of Su (隋) dynasty, Yi Yeon (李淵) and Yi Se-min (李世民), who were father and son, raised an army to defeat Emperor Gong (恭帝) of Su and founded the Tang (唐) dynasty in 618 AD.

In 626, King Tae-jong (太宗), named Yi Se-min, succeeded his father, King Go-jo (高祖), named Yi Yeon, and ushered in an age of great prosperity (盛世) under the era name of Jeong-gwan (貞觀之治, 627-649). He unified the country, expanded the territory, guarded against extravagance, stabilized the economy, recruited talents from abroad, and helped to develop the academia and the culture of the country. He became the model king for subsequent kings to follow.

Such Jeong-gwan rule was possible not only because of King Tae-jong’s abilities, but around him were wise retainers such as Du Yeo-hui (杜如晦) who was known for his decisiveness; Bang Hyeon-ryeong (房玄齡), recognized for his planning skills; and Wi Jing (魏徵), known for his upright character.

One day, King Tae-jong asked his retainers, “Between starting a business, and maintaining that business, which is more difficult?”
Bang Hyeon-ryeong replied, “Starting a business can only be achieved by only successful person among many rival leaders that spring up everywhere, so I would say starting is more difficult.”
Wi Jing gave a different reply, “From the old days, the position of a monarch is finally obtained after going through much hardships, however it is easily lost in complacency. Therefore, I think protecting and maintaining is more difficult.”
King Tae-jong nodded, and said, “Duke Bang had to risk his own life with me to gain the whole world, and that’s why he said starting a work is more difficult. Duke Wi has always been cautious against pride and extravagance for the prosperity and the welfare of people (國泰民安), and also against complacency which causes calamity and chaos (禍亂). And that’s why he has said protecting and maintaining is more difficult. Since the difficulties of a start has come to an end, I shall now focus on maintaining with you.”