Don't back up the moment you run up against a little difficulty.

不要遇到一点困难就打退堂鼓。

We've run up against a big problem .

我们碰到了一个大问题。

But this would run up against Putin and Russia's veto.

但是这会遭到普京的反对，俄罗斯会投反对票。

You can't give up the moment you run up against difficulty.

不能遇到点困难就打退堂鼓呀。

In keeping a diary in English, we inevitably run up against a lot of difficulties.

坚持用英语写日记，我们不可避免地要遇到很多困难。