Since about middle school, I have always kept some type of journal. I believe it started with the lack of friends and support system that I had in the past. Humans are naturally social creatures and when our social needs are not being met we need to find other more comparable ways of filling this deficit. Mine was keeping a journal. There is nothing like being able to write exactly how you are feeling in that very moment knowing that you are completely free of judgement from anyone because the only one who will ever read it is you. Aside from when people cross boundaries and decide to take it upon themselves to invade that part of your privacy...
in total, I have probably filled up a total of about twelve journals so far and I can genuinely say that they got me through some rough times. Not to mention, I can refer back to my journals as necessary if I can't quite remember something. Or when I feel so hopeless and defeated with whatever is currently going on in my life I can refer back to other moments in my life that were far worse as a way of reminding g myself that bad times don't last.
All in all, keeping a journal is probably what has kept me sane all these years and I couldn't imagine not having one