I write a journal of sorts as entries online. (I'm not sure if we're allowed to link or name sites here, but I will just say that it is a goal-oriented site, and I find it quite helpful in charting my progress or lack thereof.)

I used to write in a sort of diary, but I too have the fear of messing up nice new notebooks (I also have a stack of sketchbooks I don't dare to use!)

I do have a notebook I take to therapy, for the times she's set me some kind of homework, and for taking notes on important points relating to handouts or books she's lent me.