You have to persevere with difficult students.

对难教的学生你必须坚持诲人不倦的精神。

You must persevere with your English studies.

英语学习要持之以恒。

It's difficult, but I'm going to persevere with it.

难是难，但我一定坚持到底。

If you persevere with work, you'll succeed in the end.

你如果把工作坚持下去，最终会取得成功的。

If you persevere with the work, you'll succeed in the end.

如果你工作锲而不舍，最终会取得成功。