This is a fear and a paradox of doing work that's important.
A fear because so many of us are raised to avoid appearing arrogant. Being called arrogant is a terrible slur, it means that you're not only a failure, but a poser as well.
It's a paradox, though, because the confidence and attitude that goes with bringing a new idea into the world ("hey, listen to this,") is a hair's breadth away, or at least sometimes it feels that way, from being arrogant.
And so we keep our head down. Better, they say, to be invisible and non-contributing than risk being arrogant.
That feels like a selfish, cowardly cop out to me. Better, I think, to make a difference and run the risk of failing sometimes, of being made fun of, and yes, appearing arrogant. It's far better than the alternative.