It has been discovered that after the age of sixteen, the number of our brain cells begins to decrease at a speed of several million a year. They simply die off. In certain types of activity, the human brain is at its highest point in the early twenties, when it has collected enough information to be able to use the vast number of cells freely in the most effective way. Pure mathematics is one of the fields in which this happens, and we know that Albert Einstein made all his world-shaking discoveries between the age of about 20 and 25, and spent the rest of his life tidying them up and arranging them.
But in certain other types of activity (of which being an author is perhaps one), experience is more important than sharpness of brain, and there one usually finds that a person reaches his or her peak much later in life.
Besides sharpness of brain and experience, here is another thing that is very important, and that is wisdom. One can have a very quick, inventive brain and plenty of experience, but if one uses these foolishly, one harms both oneself and others. Wisdom does not always come with age ——there are plenty of foolish middle-aged people about ——but the average person tends to learn wisdom as he gets older, usually by making painful of embarrassing mistakes. Leaning to be wise is basically learning what is not possible; and what is possible but so difficult that it is not worth all the trouble one has to go through to get there. Mostly, it is learning about human nature; how real people behave and react, as against how one would like them to behave and react. One can read and hear lot of idealistic stuff about how to make the world a better place, which would be found if it was based on an accurate observation of human nature, but which is basically a waste of time because it is not.
