Wisdom often sounds less certain because it has met more exceptions.

Certainty is easiest early. Wisdom sounds tentative because it has run into the cases where the rule failed, the person who was an exception, the situation that did not fit. That tentativeness is not weakness; it is a record of contact with reality, and it is why experienced advice often sounds less impressive than confident advice.

When choosing whose judgment to trust, notice who acknowledges exceptions and who does not. And in your own speech, allow yourself the qualifiers when they are honest. It is less satisfying to say and considerably more useful to whoever is listening.