I don't keep a journal, but I do behavioral tracking on a spreadsheet. I find it helps me to see how I was responding to meds, or what sorts of triggers precipitated acting out (missing work).

I find my thoughts hard to form cohesively enough to write down without getting frustrated and erasing them... my ideas and values are often contradictory as I struggle to work out what is correct and what is false which I spend a large amount of time doing/thinking. And my days are too boring to write down really, in detail, ha!

Also, I am an artist and usually spend time doing art things rather than writing. I like the scrapbook idea...I suppose it might be a good idea for cathartic reasons... something to consider anyway.