When I was 7 years old, members of my family called me "Mr. Precise," because I corrected their grammar and usage. People who grow up to be prigs can be identified early on.
This regrettable tendency was only reinforced in later grades by Mrs. Jessie Perkins and Mrs. Elizabeth Craig, two teachers of the old school for whom there was the right way for everything, and everything else was error. Sentences were written to be diagrammed in an orderly manner, subjects and verbs smiled in agreement, and pronouns respectfully acknowledged their antecedents. Ain't and double negatives were beneath contempt. I once gave a wrong answer on a quiz, and the reaction was consternation, followed by a more-in-sorrow-than-in-anger reproach. English was a realm of certainties.
Graduate school in English removed some of the certainty, because no one since, maybe, Milton has read all there is to read. But a graduate student in English who admits to not having read any particular book loses face, so the years at work on an M.A. and a Ph.D. (even when the latter is abandoned unfinished) provide steady practice in bluffing. In the absence of certainty, the appearance of certainty will make do.
Then came work at a newspaper copy desk.
Copy editors have no illusions about anyone, because we see the work the reporters and assigning editors do, quickly identifying who is reliable and who is not. More than that, we check one another's work. We know where each colleague is strong and where he is shaky. No bluffing here.
If you watched Upstairs, Downstairs, you may recall an early episode in which the saucy parlor-maid challenged the butler, Mr. Hudson, asking why she should pay him any heed. Mr. Hudson answered majestically, "Because I am older than you, and therefore wiser, and besides, I have learnt humility."
On the nights I work on the copy desk, proofs of articles I've edited come back with errors flagged and lapses annotated. Curbside rulings I make on house style have to be revised or reversed later. Authorities I consult to resolve murky issues contradict one another. Reader complaints, full of certainty and scorn, are forwarded to me. Sometimes they are right.
Older I am. Wiser — still open to decision. But for a quarter-century now I have been schooled in humility.