Knowing the answer and never saying it is like having a key you never try in the lock.

Staying quiet when you know something feels safe, because there is no chance of being wrong in public. The cost is invisible: the group goes without what you had, and nobody ever finds out you had it. Over time people build a picture of what you can do from what you actually said. Silence tends to get read as not knowing.

Say the thing once this week in a room where you would normally hold back. You do not need to be certain, and you are allowed to say you are not. The discomfort drops sharply after a few repetitions, and being wrong occasionally costs far less than you expect.