It’s hard to speak your mind because you don’t want to hurt anyone.
That’s the main thing, I find. Don’t want to hurt oneself either, of course, but that’s not very likely in a halfway reasonable society like ours.
But the biggest things on your mind tend to be the people you know and the experiences you have with them and the thoughts you have about all of that.
Thoughts that you might not want them to hear about.
So you have to be anonymous.
And that’s not easy.