When I was a teenager, I was terrified that people would find out how much of a "pervert" I was, so I never wrote anything down. Well, once, and I ripped it up and threw it away immediately. It was the barest hint at my internal life and used my own personal coding. Nobody would have known what it meant, but I was so scared that I couldn't even call it what it was.
I had a locking diary. I still didn't trust my mother not to read my stuff if I wrote it down.