Why does almost everyone have secrets?
There is an old saying that 'Everyone is like a moon, and has a dark side which he never shows to anybody.' I guess there are a lot of different things that considered as someone's dark side secret. People have the right to keep secret on some personal matters which they don't want to receive any judgement from others.
Personally, if I hold a secret I won't share it with anyone else till the day I decide to uncover it. And I believe I can keep other's secret, it's a trust issue. I won't break my promise unless the secret is no longer a secret.
One would expect their secret be kept safe, yet this is not always the case. Take my own experience for example: I was attracted to a boy in middle school. We passed many notes in classroom. While, love and cough are not easy to hide. One day, my mother found one of the notes in my textbook. So I had to confess all to her. She laughed at me and asked me to focus on study and let go the puppy love. I agreed with her on the surface, but in fact, I still wrote letters with the boy until several years later.