"As long as you work hard, an iron pestle can be ground into a needle" means: It is a metaphor that as long as you are determined and willing to work hard, you can succeed in anything no matter how difficult it is.

Pestrel: a stick for pounding rice or pounding clothes; only: conjunction. Indicates a necessary or sufficient condition.

The inspirational story of "As long as you work hard, an iron pestle can be ground into a needle": Li Bai, the great poet of the Tang Dynasty who did not like reading when he was a child, was inspired by an old woman who was grinding an iron pestle on a stone by the river to make a needle. , understand the truth of "As long as you work hard, an iron pestle can be ground into a needle." Li Bai therefore studied hard and finally became a great poet, who was later called the "Immortal of Poetry". We should educate our children to persevere and study hard.