Among the more existential regrets I have is about not committing fully to what I want. It's easy to assign it to fear, but it's often about the lack of awareness that I now have, that I didn't have in retrospect, for whatever reason. Getting from point A to B just didn't seem possible.
But fear, even if I call it discomfort or anxiety plays a part, even today. I still have to force myself to be the person who asks a question when I don't understand something. Who doesn't just spout answers. Because I hear those people all the time, and they are often wrong and everyone in the room knows it and moves on, because it's too much effort to bother with them.
Asking questions has its downsides. It opens you up to everyone knowing exactly what your understanding of something is. Keeping your mouth shut and nodding keeps your cards closer. And you can build a career doing that. I kid you not.