That is an interesting and insightful observation.

What purpose does the filter serve?
I could be many things, all of them fears.
Cautiousness is a protective behavior, something done to protect you, and keep you safe. That doesn't mean there is danger, just that there are things that feel dangerous to you, so you take precautions. Identifying your fears while help you understand this more.

For example, for me, it could be a fear of looking/sounding stupid which encompasses a fear of not being liked or of rejection. It could be the opposite - a fear of intimacy, a fear not of being left out (because we stay out, where it is comfortable), but a fear of being included, drawn into, .. and maybe being taken over (lose our identity).

It's fun to explore these kinds of things. I don't know a lot but what I'm aware of, I learned in my therapy with a psychoanalytically trained psychotherapist.