3 sentences

1. 艰苦的环境可以磨练一个人的意志。

   jiān​kǔ de huán​jìng kě​yǐ mó​liàn yī gè rén de yì​zhì.

   A harsh environment can temper one's will.

   Source: Dong Chinese Dictionary

2. 经过多年的磨练，他的为人处世变得圆润了许多。

   jīng​guò duō nián de mó​liàn, tā de wéi​rén chǔ​shì biàn de yuán​rùn le xǔ​duō.

   After years of experience, he has become much more tactful in his dealings with others.

   Source: Dong Chinese Dictionary

3. 经过多年的磨练，他终于领略到了这门艺术的真谛。

   jīng​guò duō nián de mó​liàn, tā zhōng​yú lǐng​lüè dào le zhè mén yì​shù de zhēn​dì.

   After years of practice, he finally understood the true essence of this art.

   Source: Dong Chinese Dictionary