In order to write correct English, we have to go through a challenging task. It is to learn by heart at least three hundred exemplary English sentences. I believe when they have got throigh this, students learn to produce logical, grammatical, and idiomatic English sentences and that everyone who wants to be able to do this must go through this hardship. However, some teachers don't tell them to do so.

Recently, I came to be in charge of a new student. His former teacher got retired from work so I took the place of him. The student said he had been practicing writing English for three months, but on seeing what he wrote, it convinced me that he had not undergone the hardship of memorizing. So I told him that he needed to know by heart exemplary English sentences no matter how hard it seemed. He seemed to have known it in advance so he easily made up his mind to go through the task. 

Pointing out a person's demerit face to face with that person is often challenging. Nevertheless, students want to make progress so we have to do it. We must endure first before they endure.