这是我觉得很困难的一件事。当我离开时，我十分十分想念我的女儿。不过当我们团聚的时候，这段时间很特别。

It's the one thing I find very difficult I miss my daughter hugely when I'm away. Its also makes the time together more special.

youdao

Somehow, when I told you to invert the transformation, some of you had some difficulty.

我上次让你们逆推变换公式的时候,有的同学觉得很困难

耶鲁公开课 - 基础物理课程节选

So I think that it's true that the economy is difficult and there is big challenge in front of us.

所以我觉得，目前的经济形势真的很困难，我们面临着很大的挑战。

事业就是挑战 - SpeakingMax英语口语达人