one should not leave things unfinished
Proverb derived from a story about Mencius' mother, who cut a cloth she was weaving to admonish her son for leaving school early. Used to emphasize the importance of perseverance and completing what one starts.
See also: 断機
The lesson of Mōbo Danki is an admonition that one must not give up halfway.
Refers specifically to the act of cutting the cloth in the story; 孟母断機の教え is the full proverb expressing the lesson derived from that act.
From a classical Chinese tale about Mencius' mother, who cut a cloth she was weaving to teach her son the importance of not leaving tasks unfinished. The phrase is a direct reference to that story.