The first time I started struggling with mental illness (at 17/18) I started journalling because I couldn't figure out what else to do with the anger and the fear. And I journalled hardcore for a number of years after that, but then I stopped, mostly due to a life of addiction. In recovery I have continued, somewhat sporadically. I had a journal entry yesterday that was very therapeutic for me. I find it a great tool for me to deal especially with anger, or hopelessness, or being fed up.