idiom · highly polished and refined through intensive effort and numerous revisions, especially of a literary work

这部名著的语言经过千锤百炼，极其精炼。

idiom · thoroughly steeled or toughened by enduring many hardships and the vicissitudes of life

优秀的领袖都是在艰苦的环境中经过千锤百炼而成的。