I never kept one. The idea just doesn't appeal to me. I know writers who use journaling as a useful writing tool, but for me, the small details of my very quiet, boring life just don't work as a springboard to creativity.Besides, I don't want my children reading an old diary and thinking "Golly, mom was so boring.". I think I have them fooled right now, so I need to preserve the illusion.
In clearing my dad's house, I found a diary kept by his brother during his years as a cadet at West Point. His brother was killed in 1952 in Korea, so I have no idea why it didn't go to his widow. I'm guessing she returned it to my grandmother after she remarried. Anyway, it's pretty boring stuff. Mostly, he lists what subjects he studied, exam grades, PE activities, and the names of movies he saw. Girls are sprinkled in here and there, including one named Jeanne Anderson. Jeanne, if you are still with us, I want you to know you looked really, really hot in that one-shouldered black ball gown. And he was crazy about you for at least a month.
With electronic communication dominating our connections with each other, we don't leave written records to be passed down to our heirs. Letters my grandmother, then my father, saved from her dead son still exist for us to read today. They're certainly not earth shattering, but they come from a long-gone place and time. I have enjoyed "hearing" from the uncle I never knew. I think I'll keep them, too.