I've kept journals off and on for decades. Sometimes I write long paragraphs about thoughts I'm having or things I've experienced. Sometimes it's lines of poetry or random phrases that for whatever reason get stuck in my head. My only rule is no rules - write down anything at all for any reason.
However if you're journalling to deal with a specific emotionally-loaded event or process, like HBG, I can see how it would be very useful to have some sort of guiding questions that you try to answer in your writing. Maybe you could generate a list of guiding questions yourself, or maybe there are some recovery-oriented journaling guides? If you're interested in some sort of twelve-step work, maybe take different steps as prompts for your writing?