The author of Tensei-jingo says in his column that he had a composition lesson for several years with hundreds of people, who were men and women of various ages.
Every week he assigned a subject and students had to write compositions on the subject. While reading all these compositions he found out that there might be two types of having interests. Besides the types seemed to depend on their ages.
Roughly speaking, younger people have an interest in a new thing, and write various sentences from the new point of view every time. Older people, on the contrary, have one or two important themes in their minds. So their thinking and writings are always around their own themes, even though they are given a common subject.
For example, if the subject of this week is whose theme is "watch", and next week "letter", the man whose theme is "war" will write about the watch of a person killed in war, and about the letter from the battlefront.
And the author says the dividing line seemed to be the age of thirty-five, of course with exceptions.
This opinion is very interesting when I think of my sentences. When I was younger and I had to write something in certain theme, I was very afraid that I was inexperienced and didn't know much about the theme. So I managed to write something after some research and consideration even with some anxiety. But now I am a little confident that there are so many ways of thinking and my poor opinion might have some stimulation for others, and so I have made up my mind to say what I think in my own way.