to endure (ren)

"Ren" means to endure. It is made up of two words, knife and heart: The knife is sitting on top of our heart.

It means when we practice endurance, we will suffer acute agony as if our heart is stabbed by a knife, however, we still have to persist.  The more we can endure, the greater our achievements will be. There is a saying in Chinese: Gold is form from incalculable endurance.