I started keeping journals when I was fourteen and at last count had nearly a thousand. They come in all shapes and sizes, from little pocket ones which I carry around with me to enormous tomes. I always keep a notebook by my bedside, for dreams as well as nighttime thoughts, and I try to have one by the swimming pool or the lakeside or the seashore; swimming too is very productive of thoughts which I must write, especially if they present themselves, as they sometimes do, in the form of whole sentences or paragraphs.
. . . The act of writing is an integral part of my mental life; ideas emerge, are shaped, in the act of writing.
My journals are not written for others, nor do I usually look at them myself, but they are a special indispensable form of talking to myself.Oliver Sacks, On the Move: A Life (New York: Alfred A. Knopf, 2015)