Hi,
I find it very useful to post on my diary everyday, more for me than anything else!
It's a place you can record your thoughts, feelings, ups and downs!
It is also very good to read back over previous days, weeks, months or even years (!) to help you understand your moods, what motivated you and what made you sad.
Even if no-one reply to my rambling diary, it's the one place I am totally honest, telling you lot things I won't even tell my dh!
So, in my opinion, go for it!