There are two kinds of "secrets once sworn to keep": those sworn to someone else, and those much darker ones sworn to yourself to never be revealed. Those first ones are easier borne but those dark and unspeakable ones must remain in the dark depths of consciousness. Those closer to the surface may be revealed with the passing of time, but the dark ones, never.

Ask someone who has been in combat and they will not talk about details. Those are the real secrets which remain in the dark.