I have been journaling for YEARS!!! I think they go back at least ten years. But it's not a daily or regular thing with me, at least not as often as I used to. My entries tend to be on the depressive/irritable side because I just need to get those feelings out. If I find myself ruminating over something, I'll write it out in my journal. Yesterday I was pissed off about something and those thoughts would not leave my mind, so I wrote it all out, curse words and all, and I was able to calm down. Journaling may not be for everyone, especially if you have trouble verbalizing your feelings, but it's one of many stress relievers for me.
Oh and they're not all completely depressing. There are a handful of happy entries too.