I have always written stuff down to clear my head but I always just rip it up and toss it away afterwards and don't keep a diary as such because I don't want anyone to read it. It did often make me feel better to write stuff down but I always just felt I was going over the same ground repeatedly.
I recently got a password protected diary app for my pc and have started writing in depth about some of the stuff, habits and experiences in my life that bother me. I'm also keeping a kind of log of my behaviours to make myself more aware of how I spend my time, how act, what I prioritise as opposed to what I actually want to put my energy into.
I think it is too soon to know if it will work or help but I suppose I hope that by having a safe space to put all that stuff down, to assess and so on that I might be able to help myself overcome some things.
Anyone else done this, did it work? Any techniques or books to recommend?