Photo: The Canadian Press

For nearly 100 days, President Donald Trump has rattled Washington and been chastened by its institutions.

He's startled world leaders with his unpredictability and tough talk, but won their praise for a surprise strike on Syria. He's endured the steady drip of investigations and a seemingly endless churn of public personnel drama.

"It's a different kind of a presidency," Trump said in an Oval Office interview with The Associated Press, an hourlong conversation as he approached Saturday's key presidential benchmark.

Trump, who campaigned on a promise of instant disruption, indirectly acknowledged that change doesn't come quickly to Washington. He showed signs that he feels the weight of the office, discussing the "heart" required to do the job. Although he retained his signature bravado and a salesman's confidence in his upward trajectory, he displayed an awareness that many of his own lofty expectations for his first 100 days in office have not been met.

"It's an artificial barrier. It's not very meaningful," he said.

But he acknowledged that being commander in chief brings with it a "human responsibility" that he didn't much bother with in business, requiring him to think through the consequences his decisions have on people and not simply the financial implications for his company's bottom line.

"When it came time to, as an example, send out the 59 missiles, the Tomahawks in Syria," Trump said of his decision to strike a Syrian air base in retaliation for a chemical weapons attack. "I'm saying to myself, 'You know, this is more than just like 79 (sic) missiles. This is death that's involved because people could have been killed. This is risk that's involved.'"

"Here, everything, pretty much everything you do in government involves heart, whereas in business most things don't involve heart," he said. "In fact, in business you're actually better off without it."