She struggled hard to master her temper.

她竭力按住性子，不发脾气。

《牛津词典》

It is really hard to master a language.

要掌握一门语言谈何容易。

youdao

I think it hard to master a foreign language.

我认为掌握一门外语是很难的。

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

But the split would leave Netflix with one business that is probably going to shrink DVD-by-Mail and another that ought to be growing fast but is going to be hard for Netflix to master.

FORBES: Netflix's Split Won't Cure Its Online Streaming Ills

In fighter pilot training school he had to practice twice as hard as others to master the same maneuvers.

FORBES: Robert Greene: How to Become the Master of Any Skill