Why I pen down my thoughts in the diary

I write diary and consider it as a reference for the future. I do not write daily. I write about once in two months. And when I look back at the entries, I feel so good. For me my past has always been more impressive than my present. I read those entries and think what wonderful moments I had, what wonderful life I had, even though the present is as happy as the past. And when I will read today's entries in the future, once again I might feel the same.
I was reading this article: Six reasons to keep a diary: http://news.bbc.co.uk/1/hi/uk/2289919.stm
The article says that your diary can be a loyal friend and can also be a nice gift for your grandchildren. I can't consider my diary to be a loyal friend because I always fear that someone would read it. But yes, I do feel lighter after I write down a part of what is in my mind. And if I grow old before dying, I would look back at my diary and assess it. If it is worth leaving for my grandchildren and great grandchildren, I would definitely do that. But for the time being, its just for me.