that's the secret I would never tell

Someone asked me to tell him the story
which nobody knows, about me. The secret that nobody knows.
so I said,
If it's the secret that nobody knows,
it is literally the thing that nobody knows, which means,
I would never tell.
but for a very short moment,
I confused myself what is the secret that nobody knows about me.
What is the deepest secret inside of me. what is it?

I figured out that I don't even know myself very well.
How could it be possible to tell you about me?