He knows not when to be silent who knows not when to speak.

Silence and speech are the same skill read from opposite sides. Someone with no sense of the right moment to say something will be equally unreliable about when to hold back, since both depend on reading what the situation actually needs. It is judgement of the room rather than a personality trait.

Practise the reading rather than the rule. In your next conversation, ask what is actually wanted here before you either speak or stay quiet. Getting that right occasionally is more use than a policy of always saying less.