I have three journals that I'm currently keeping up: A dream journal, which really is interesting and helpful (for evaluating the health of my psychological state, hah). I've only really started focusing on maintaining it for this last month. A day-to-day journal, which just holds my average retelling of my daily encounters. I've had this one for several months, but never had the patience to maintain it. I also throw in any poetry or stories I write, and I keep it on me most of the time for that purpose. And finally a reading journal, which isn't really as sophisticated as it sounds. I mostly just use it to keep track of books I'd like to read, and crossing them off as I finish them. It's satisfying to see my progress on the list. I've had this one for over a year, and it's the one I use and read most frequently.
I'm a big fan of the multiple journal approach. I keep one with me at all times to write down thoughts that occur to me over time, and then I also keep a journal to keep track of thoughts related to books I'm reading. I've found that the biggest benefit to keeping a daily journal is that it helps me be more observant. I'm more aware of events and places surrounding me. I've noticed more in the past year than ever before.
I used to keep a dream journal! While it was a lot of work to force myself to scribble out everything I could remember whenever I woke up during the night or first thing in the morning, it was one of the most interesting things I have done. I found myself beginning to remember multiple dreams every night. After probably 100 entries I finally was able to realize when I was dreaming and become lucid, but I always woke up shortly afterwards. I was never able to gain control of my dreams or change things, but that was my goal. If I hadn't experienced it myself I don't' think I would have believe lucid dreaming was real. I stopped when work became busy and I wasn't getting enough sleep and needed to just focus on that. I should start again though. Have you ever had lucid dreams?
I definitely have, but I can't seem to tell if that was from keeping the journal or not. I've had several dreams where I'd perform reality checks that would lead me to the conclusion I was dreaming. The concept is that if you make a reality check (like checking the number of fingers you have) a normal, frequent part of your life it will logically begin to appear in your dreams, making you realize that you are in a dream and ultimately lead to becoming lucid. I wanted to try this out, but I never was able to maintain the constant reality checks, and dream journalling has always led to vivider dreams I could actually remember (and requires a bit less commitment).