Confidence that needs to announce itself is usually just nerves wearing a costume.

Steadiness does not need witnesses, so it usually stays quiet. Announcing is a way of asking a room to confirm something you have not settled inside yourself, and the bigger the claim, the more confirmation it is fishing for. That works in both directions. It explains the person in your grade who keeps mentioning how little they studied, and it explains you on the days you overexplain.

When you notice yourself building the case out loud, stop and ask what you are hoping somebody will agree with. Then say the smaller, truer version. It costs less and it holds.