I've been consolidating some old journals and for the past three years have been keeping a recent one, and what strikes me is how often a journal entry will cover something I've totally forgotten. Sometimes the entry sparks a memory--it is still there, though I haven't thought about it in years. Other times the memory stays lost. I might discover I went to a party on a certain night when I was 22, but still remember nothing about that party.
Writing captures so much that we might otherwise forget. I make a note today that the snowdrops are blooming now, a harbinger of spring--a small detail I'm sure I would never be able to date in the future without my journal. It's a choice, of course, what to record and what to leave out. Of all the moments I lived through today, I will capture only a few of them. I polished an essay, took a walk with a friend, noticed the snowdrops, ate a turkey sandwich. I don't know which of these details might matter to me in years to come, and we can't live entirely for the future anyway, can't preserve everything.
So I write down the first things that come to mind--sometimes from world news, usually from my personal life. Sometimes major, sometimes trivial. I strew bread crumbs for my future self to follow. But it isn't only about the future. The act of jotting a few notes each day makes me pay closer attention to the present. It requires me to stop and observe, at least for a few minutes.