I have tried to keep a journal multiple times. I tend to fail when I do though. I usually just forget to write in it and then remember it months later.
Though when I was deployed to Afghanistan I kept one fairly regularly. That is the only thing in it is my experiences there. I think I even let my family read it. I have it in a box somewhere.
I tried keeping one recently, since my big break up, But I keep forgetting about it. Plus I don't have anything interesting to add to it.