Rabbi Yisrael Lipkin of Salant
The head of a large company turned to R’ Yisrael with the following question. He had only one hour free a day to learn. What should he learn during that time? “Spend the hour learning Mussar,” answered R’ Yisrael. “If you do so, then you will discover many more free hours in the day.”

From Sparks of Mussar by R Chaim Ephraim Zaitchik