i've been keeping a kind of patchy journal for a few years now, its good to look back on the earliest entries and laugh at how mental i was and how i've kind of grown. the later entries are also good because they remind me of the even keel i was on at the start of this year when i have a depressive turn and start behaving irresponsibly.
its not all thanks to the journal, of course, but keeping track of your mental state and building a sequence of events in your life is important for staying grounded in reality imo. i can look through the pages and find bad entries, remember my state of mind then and associate it with thoughts in the present, which indicate that the train of thought i'm on leads to auschwitz