Few men make themselves masters of the things they write or speak.

Most opinions are held at a shallower depth than the confidence attached to them suggests. People speak and write from a general impression, a half-remembered argument, the shape of what everyone around them says, and the fluency of the delivery hides how thin the ground is. Genuine mastery of a subject is rare and takes an unfashionable amount of time. Fluency is not the same as knowing.

Pick one topic you regularly hold forth on and test whether you could explain it properly to someone who pushed back. Where you cannot, either learn it this month or speak about it more carefully.