I’m one of those English instructors who believe in requiring students to regularly write an English diary. It’s not that I’m the stern taskmaster who believes in piling reports, other assignments and a lot of busywork on the poor students. The reason is that I see regular writing practice as one of the most effective ways of improving a working knowledge of the language.
A regular and frequent use of any skill is the surest way to improve the quality of the skill. Regardless of how bright or talented any one of us may be, working at and practicing almost anything is the way to improve. Communication and language skills are not an exception to the rule. The more you listen to English media and English speakers the better you will become at listening. The more you read in English, the better you will become at reading and the more you write, the better writer you will become.
The problem is that it takes some discipline to plan time and organize your thoughts in order to put them down on paper. The solution is to establish a daily (or weekly) routine and make up your mind up that it has the same level of importance as some of the other necessary daily chores. Make your bed, brush your teeth, wash your face and write a couple sentences in the diary.  Small tasks just seem easier to accomplish than large, time consuming jobs.
I ask my students to write only one page a week. If done daily that adds up to only two or three sentences a day. The point is that daily you organize some thoughts in English and put them down on paper (or on your computer notepad). The value comes from the daily routine. Refreshing and expanding any kind of knowledge on a daily basis is like planting a seed and letting it grow.  It won’t take too many weeks before you have a growing seedling and eventually you should have a thriving and well developed skill.
The students in my Freshman English classes have come to expect me to ask them about their English diary writing just about every class meeting. I actually make it a bit of a joke because we all know that many of the students don’t write regularly. The ones who have learned how to manage their time and do the writing regularly will have steadily improving writing skills. The students who spend all night writing many pages of weekly diary just before the due date don’t show much improvement. They just show tired red eyes and have difficulty staying awake in class.