Sometimes President Trump did not seem to understand that concept.
You have absolutely not understood what was happening. His news coverage was 95% negative. He would stub his toe and the media would scream that he had Russian doctors inject him with bleach while prostitutes were urinating on him to resolve the issue.
And besides most of what the media hammered him on for tweeting was the truth, but you want him to keep his mouth shut. There was no Russian Collusion, Mueller was not only corrupt but also had dementia, Comey should have been fired and leaked classified materials, FBI did try overthrow a sitting President, Intelligence agencies leaked and lied to the press, the justice system overwhelming attacked conservatives (unbalanced beyond imagination), there was massive voter fraud, intelligence agencies spied on his campaign, the list goes on and on.
Which one these items would you prefer he kept his mouth shut on?
I think you are in denial about the damage that President Trump sometimes caused himself. On more than one occasion good news for the administration in the morning had been overshadowed by a controversial Trump comment or tweet by the evening news cycle. More than once I wondered what the heck he was thinking when instead of taking a victory lap, he instead lashed out at someone or brought up some totally different issue. Good news in politics must be managed and cultivated so as to get the most mileage out of it. President Trump just never seemed to get that concept. I don’t know if he was not focused on those occasions but he wasted many good opportunities. Yes the media was totally against him, we all know that but some days he also worked against himself. He is a good businessman and was a good President policy wise but too many times he was not very savvy in managing the public perception of him. We will all vote for him given the chance but he needs more than just us to buy into the program.