There was, I can testify, a lot more drinking in Washington, D.C., before May 15, 1978. That was the date, through the grace of God, that I had my last drink of beer or booze or wine.

Previously, I had given up drinking at different times, for Lent or to lose weight (a waist is a terrible thing to mind), always to return for another round. But what changed my ways — beyond a miserable hangover while playing hours of duck, duck, goose with a dozen happy kids at my daughter Amy’s sixth birthday party — was the eloquent example of my very close friend and favorite ex-drinking partner. John R. never sermonized. He never condescended. John R. gently but convincingly told me that my drinking was keeping me from being a better husband, father, friend and employee.

All of which brings us to the case of Piers Morgan, the British columnist and TV host who has been friends with President Donald Trump since at least 2008, when Morgan won the season finale of NBC’s Trump-hosted “Celebrity Apprentice.” On Twitter — which is the president’s preferred means of communicating his feelings and insights to the world — Trump follows just 47 other individuals, one of whom is Morgan.

During his presidency, Trump has done a total of three interviews with British television. All three were with Piers Morgan, who, while being occasionally critical of Trump’s position and hyperbolic language, has been a defender of the 45th president against his legions of British belittlers.

So, what a surprise when Morgan went on “Reliable Sources” on CNN, where he had previously hosted a prime-time show succeeding Larry King, to do what those familiar with addiction could only call an intervention. Morgan said, “On almost every level … Donald Trump, at the moment, is failing the American people,” directing his censure toward the almost-daily White House press briefings, which he has watched “with mounting horror.”

“He’s turning these briefings into a self-aggrandizing, self-justifying, overly defensive, politically partisan, almost like a rally, to him — almost like what’s more important is winning the election in November.” Directly addressing his friend in the White House, Morgan added, “You will win the election in November if you get this right. If you stop making it about yourself and make it about the American people and show that you care about them over yourself, you will win. And, conversely, you will lose the election in November if you continue to make it about yourself, you continue playing silly politics, continue targeting Democrat governors because that suits you for your electoral purposes.”

Trump’s self-absorbed performances at the White House briefings — the abusing of reporters whose questions he does not want to or cannot answer, the whining about the appreciation he deserves and does not get, the self-congratulations for the superb job he and his administration are doing — are hurting him politically. Public trust and confidence in the president’s leadership are falling. It’s not working. The question: Is Donald Trump wise enough and big enough to accept the brutally frank advice of a close friend?

• Mark Shields is a columnist with Creators Syndicate.