There is something interesting about writing diaries... I was forced to write it when I was very young, probably about the same age when you started yours, but I just found myself documenting the most mundane things because it seemed more like a chore than anything else.
It took someone to give me a 5 year diary and a nice fountain pen for me to pick up the habit again almost 20 years later... But I have found that the mind can be a very tricky customer when it comes to putting down your thoughts and reflecting on what you think you were thinking when you were thinking about what to write down (if that makes any sense at all).
The wonderful thing about these 5 year diaries is you can compare the same day over a number of years and see whether you end up going out and partying every new year's eve... what you did for Valentines Day or your birthdays (I don't celebrate them anymore) and see whether you live in a constant cycle or if it evolves along the way :)
I'd love to know where you keep your diaries and how often you look back at past events and come up with new revelations!
It's never too late to start keeping diaries! I think that the most useful aspect is being able to keep track of who you are as a human and how you've gotten there. It's illuminating to read back and self-psychologize. It tells you more about why you do the things you do than is probably comfortable for most people. I keep my diaries in a big old chest in the corner of my room. Occasionally I'll pick one up and start reading. It can be pretty emotionally overwhelming.
The problem with keeping these thoughts on paper is that I have to realize that my documentation of the events are subject to my feelings at the time of the event, which is far from being a faithful and objective recollection of the moments of my life. And because I know this it is also difficult to compare one moment to another because the way I think about things also change overtime. So what can I really take out of reading these thoughts? I guess one thing that is clear are some of the cycles that you go through in life, which for me is mostly to do with changing jobs and changing location, and the emotions that I go through during these transitions.
Are you one of those people that write about ideas, thoughts, events or just anything that comes into your head at the end of the day? Do you write your diary just before you go to sleep? Have you missed entries before, and if so why? Do you use a special pen for your diary entries? So many interesting questions, and not a single one about the diary itself :D