Vita Sackville West once wrote
It is necessary to write, if the days are not to slip emptily by. How else, indeed, to clap the net over the butterfly of the moment? For the moment passes, it is forgotten; the mood is gone; life itself is gone. That is where the writer scores over his fellows: he catches the changes of his mind on the hop.
Similarly, the late Thomas Merton wrote:
Keeping a journal has taught me that there is not so much new in your life as you sometimes think. When you re-read your journal you find out that your latest discovery is something you already found out five years ago. Still, it is true that one penetrates deeper and deeper into the same ideas and the same experiences.
I think when I was younger, I misunderstood the purpose of journaling, thinking that the goal of such an exercise was to record what you did. Certainly I was not the only one to confuse the purpose of keeping a calendar and keeping a journal or a diary. I now understand that to be a good diarist is to record my feelings and reactions, and as Merton and West illustrate, to so faithfully enough that I can recognize patterns and cycles, for good or for ill, and should I choose to, to try to change relationships to things, people, and so on.
I am not always good at being faithful to my habits, especially when they are good for me. I have read the diaries of Plath, the deeply personal writings of Nouwen, and of course the confessions of Augustine so many times that my own copies are threadbare. I would think I could at least stay faithful to writing my own for at least two years. Who else is willing to commit?