Talking about diary, I used to keep them when I was single. I went through some painful phases and jotted them down. However, when those sad moments were over, I would tear off the pages, leaving only the happy parts.
So, when I look back at the diary and saw so many torn pages and in there, left only a few pages, I know that I can't lie to myself. Those pages may be gone but scars remain. So I guess it is foolish to keep a diary after all. You can tear all the pages you want but at the end of it, the effects remain.
Which is why I never go to the extreme on my blog. What have been seen by others cannot be hidden.