I have been keeping a personal diary since I was about 13 years old. It's my private space to reflect on experiences, thoughts, emotions. It helps me to manage stress, anxiety! I highly recommend this practice!
Took up journaling late last year on Julia Cameron’s suggestion (“The Artist’s Way” prescribes for artists a daily, morning free writing exercise). It is a distinctly effective way to neutralize ruminating thoughts, pull apart confusing feelings, de-censor myself from myself; simply put, I have been able to raise my consciousness through journaling.
I wouldn't do it out of fear that someone else might find it and read it. Having been witness to the fallout of such an event, friendships were ruined, a relationship ended, and there was much emotional pain.
Some things are just best kept inside one's own head.
I'm partial to burning my journals after some time. It's highly cathartic to see your thoughts and feelings scribed onto the page and removed from existence, as if to underscore the fleeting, temporary nature of them.
Such thoughts never do more harm than when they are trapped in our heads. Fortunately, paper notes, unlike digital ones, can be made to disappear without a trace.