WASHINGTON — President Trump has gone overseas to embark on some of the most consequential diplomatic negotiations of his tenure, threatening an all-out trade war with allies and seizing a chance to make peace with a nuclear-armed menace.

But back home, he left behind a West Wing where burned-out aides are eyeing the exits, as the mood in the White House is one of numbness and resignation that the president is growing only more emboldened to act on instinct alone.

Mr. Trump, a former reality television star, may soon be working with a thinned-out cast in the middle of Season 2, well before the midterm elections. Several high-profile aides, including John F. Kelly, the president’s chief of staff, and Joe Hagin, a deputy of Mr. Kelly’s, are said to be thinking about how much longer they can stay. Last week, Mr. Kelly told visiting senators that the White House was “a miserable place to work,” according to a person with direct knowledge of the comment.

The turnover, which is expected to become an exodus after the November elections, does not worry the president, several people close to him said. He has grown comfortable with removing any barriers that might challenge him — including, in some cases, people who have the wrong chemistry or too frequently say no to him.