And based on his fine performance at the second presidential debate on Thursday night, it looks like Donald Trump has finally learned that important lesson, too.
The president proved he could listen to what Joe Biden said and then carefully respond to what he heard instead of instantly reacting and interrupting or talking over Biden.
Of course, the president was forced to behave in part because the debate commission added a mute button that allowed each candidate to have two minutes of uninterrupted time to answer the opening question of each topic.
The mute button acted like an electric dog training collar. It didn't have to be used, and it was invisible, but, ironically, it turned out to be a great blessing for Trump.
It kept him under control and helped to keep him from hurting himself by repeating his overly aggressive tone and off-putting performance in the first debate.
Like most of the professional pundits on FOX and CNN, I think the debate itself was a draw.
But I gave the president the overall win for one big reason: After this debate you didn't walk away thinking he was a complete jerk.
As I told my son Cameron, if the president had behaved like he did Thursday night for the last 3Â½ years, the polls would be 60-40 in Trump's favor and the election would be over right now.
Overall, President Trump did everything he needed to do to help himself and unmask poor Joe Biden, who looked and sounded like an old, tired and befuddled politician from 1978 — which is what he is.
He abided by the new debate rules and was subdued, but he was still tough. He was on target. Heck, at times he actually looked presidential.
He defended himself on how his administration has handled the Covid-19 plague and helped blacks on prison reform and economic Opportunity Zones.
He touted his economic successes, stressed that the country has to learn to live with the coronavirus and repeated his pledge there will be no more lockdowns.
Trump scored major political points with voters in Texas and Pennsylvania by jumping on Biden's politically foolish statement that he plans to transition away from the oil industry.
Most important, President Trump consistently gave Biden plenty of time to hang himself while hitting him and his new leftwing ideas with good right-hand jabs.
He baited Biden into committing one of his biggest blunders of the night, getting Biden to defiantly declare, "I never said I opposed fracking." Several video tapes prove otherwise.
Biden threw the oil industry under the bus along with his old boss Barack Obama, whom he blamed for never solving the immigration problem in eight years. And I'm sure Obama loved hearing his old VP call his new healthcare plan BidenCare.
As we knew he would, Trump also made sure that the readers of the New York Times, the watchers of CNN/MSNBC and the listeners of NPR — whose biased journalists have refused to cover the exploding Hunter Biden scandal — were introduced to the sleazy finances of the Biden Family International Pay-for-Play Racket.
The irresponsible liberal media can continue to protect their "Big Guy" from scrutiny and pretend Hunter’s laptop is Russian disinformation, but for millions of the potential voters watching, Trump effectively pinned the charge of political corruption on "Ten Percent Joe."
Everyone agrees the second debate was pretty good in terms of informing voters.
Everyone agrees that despite Trump's tweeted concerns, NBC journalist Kristen Welker did an excellent and fair job as moderator — and put Fox's Chris Wallace to shame.
But Trump clearly benefited the most from the debate.
His campaign will be able to pull half a dozen damning Biden soundbites for its TV ads.
And I hear that the president's staff has finally found a way to keep Trump from hurting himself. For the next ten days they're going to install a mute button at his press conferences.