Washington (CNN) If Donald Trump has learned any big lesson in his 84 days as President, it's this: The job is way harder than it looks.

In an interview with The Wall Street Journal released Wednesday night, Trump admitted that he had underestimated the complexities of the relationship between China and North Korea. He learned from Chinese President Xi Jinping, Trump explained, that China simply can't eliminate North Korea's nuclear capabilities.

"After listening for 10 minutes, I realized it's not so easy," Trump said. "I felt pretty strongly that they had a tremendous power (over) North Korea. ... But it's not what you would think."

Trump was forced to acknowledge a similar oversimplification when it came to his attempts to overhaul the nation's health care system.

"Now, I have to tell you, it's an unbelievably complex subject," he told a group of governors at the White House in late February . "Nobody knew health care could be so complicated."

Back in late November 2016, when Trump had barely begun to wrap his arms around the prospect of being president, former House Speaker Newt Gingrich recounted that Trump told him, " This is really a bigger job than I thought.

Not immediately grasping the enormity of the presidency is not unique to Trump. It is a job -- in terms of power, scope, responsibility and expectation -- that has no parallel in the country (or maybe any other). No one is totally ready to be president on day one -- no matter what they say on the campaign trail.

But Trump is an extreme example of this "not totally getting it" phenomenon due to his unique background as a political candidate. He is the first president ever elected who had never served in the military or in elected office prior to his victory.

JUST WATCHED Trump reverses view on campaign statements Replay More Videos ... MUST WATCH Trump reverses view on campaign statements 02:48

That lack of experience in politics was a major part of Trump's appeal to voters on the campaign trail. They hated Washington and everyone in it. It was past time for a change and Trump, a successful businessman who shared their disdain for politics as usual, embodied that change.

Trump, emboldened by his early success, actively rejected the traditional preparation process a candidate undertakes in the event they are actually elected president. Rather than detailed policy proposals or briefing books, Trump read polls and stories about himself. He actively rejected the need to overthink things; he believed that a reliance on his gut and his highly-attuned sense for what people wanted and when they wanted it was all he needed to be a successful candidate and president.

His first 80-plus days in the White House have proven the miscalculation at the root of that belief, marked by the failure of his health care plan and historically low poll numbers. As a candidate -- even one for president -- you can say and do pretty much whatever you like without much consequence. You can take absolutist positions and paint the country and the world as simpler than it is.

"All I can say is it's very simple, very easy," Trump famously said about disentangling himself from his business empire. It wasn't -- and neither is the presidency more broadly.

If you are a Trump ally -- or an optimist more broadly -- you see his willingness to adjust (or reverse) positions he staked out during the campaign as proof that he is open to new information and continues to learn how to be president.

If you are less favorably inclined to Trump, his bafflement that the world is more complicated than he originally thought is a reason for serious concern about how and where he will lead the country.

What's beyond dispute is that Trump had very little idea what he was getting into during the campaign for president. Now that he's in the thick of it, he'd better be a fast learner -- or run the risk of being left behind.