What is the meaning of 磨练?
磨练： temper oneself hard


在身为罗马奴隶的艰苦磨练中，宾汉变得更强壮、更有耐力。

Ben-Hur's years of enduring hardship as a Roman slave strengthened him and increased his endurance.

唯有艰苦磨练才能强化心灵

only through experiences of trial and suffering can the soul be strengthened

Sometimes, you might see 磨炼(smelt) instead of 磨练(exercise/training). There are some disputation on which one is correct. But main idea is that 磨炼 is sort of wrong words, but you may understand it as a synonym.