Sujin, good move!
I've been keeping journals for about ten years. I thank my T for encouraging me to do that. It's been a lifesaver for me! I carry it with me in my purse! I've filled up a few dozen notebooks already! Journaling is a great way to release tension, express emotion, jot down thoughts or ideas I fear I'll forget, etc. From time to time I'll reread an old journal to track my progress, and it feels great!
Now that I have a computer I journal on "word", and still carry a little notebook with me when I leave the house.
As to someone reading what I've written: I've shared my journaling with my therapist, at times. And the more I come to self-acceptance, the less I fear being exposed. Yeah, I'd not want someone to find and read my notebooks, but hey, if they do, I'll get over it.
Best of luck on your new endeavor!