I can only answer this for myself, being an alcoholic myself. I think journaling is a good idea for everyone though.
I write down my thoughts whenever I feel the need to. Sometimes it's several times a day, several times a week or some weeks without writing anything down. Mostly I write down whenever I feel like I understood something about myself, my thinking patterns, how my past plays a role in that, what I want to change and how I could improve. Sometimes I leave that open though when I haven't found an answer yet.
If I feel really horrible I just write down my thoughts, whatever is bothering me and why. But I try to keep my journal positive or at least insightful so I try to write down why there is no need to be angry, frustrated or worried or whatever I am. It helps me grow and get to know myself I find.
My RABF writes journals too, obviously I haven't read them but he told me he mostly writes down his negative thoughts, just to get them out, his worries and stuff like that. He used to journal his moods every day when he had bad depressions so he would see on a really bad day, when it felt like his whole life was a never ending sadness, that for example he had a really good day two days ago and also two okay days that week. I haven't done that kind of journaling yet, to me it's mostly a Q&A about myself. Pages have titles like "about procrastinating and being scared of failing" or "what helps me with cravings?" "Positives about today""why I shouldn't drink again" "on worrying and prioritising" "progress I made so far"
There's really no right or wrong, it's highly personal, so maybe just write down whatever you have on you mind and want to remember in the future or would like to tell someone. Often I start writing, when I feel confused or overwhelmed and it helps me to sort my thoughts and see things clearer again.
