She struggled hard to master her temper.

她竭力按住性子，不发脾气。

《牛津词典》

To master a foreign language like English requires hard work, so you can't study too hard.

掌握一门像英语这样的外语需要勤奋学习，因此你再怎么努力也不为过。

youdao

Seven long years, he had worked hard for his master.

他为他的主人辛勤工作了七年。

youdao

And so he explains to the master: I knew thou was't an hard man which reapest where thou sowedst not and gatherest where thou strawest not.

他对主人解释：,我知道你不是个努力的人,你收获不是你播种的。

耶鲁公开课 - 弥尔顿课程节选

It's always hard to say how much this kind of personal branding contributes to the success of a business, especially one like fish-farming that's easy to enter but hard to master.

FORBES: Magazine Article

When he first moved into management he proved to be an equally hard task-master.

BBC: Time mellows football's hard man

And, if he still has the relentless desire for success he had as a player, the 50-year-old Glaswegian will prove a hard task-master.

BBC: SPORT | Football | My Club | Motherwell | McGhee out to make his mark