President Donald Trump. (Alex Wong/Getty Images)

Richard Haass is president of the Council on Foreign Relations and the author of “A World in Disarray: American Foreign Policy and the Crisis of the Old Order.”

President Harry S. Truman once predicted that his successor, Dwight Eisenhower, would have a rough time in the White House. “He’ll sit here, and he’ll say, ‘Do this! Do that!’ And nothing will happen. Poor Ike — it won’t be a bit like the Army. He’ll find it very frustrating.”

(Adriana Usero/The Washington Post)

What Truman was getting at is that all presidents bring to the Oval Office an outlook shaped by their unique personal and professional experiences — and that these experiences can become something of a liability if a president assumes that what worked in one context will automatically translate into another.

President Trump is no exception. He brings to the White House a lifetime in business and real estate, much of which is described in his book “The Art of the Deal.” The potential problem for Trump is that a businessman in a field such as real estate has the luxury of approaching deals in isolation. One can choose not to work with the same seller or buyer again. By contrast, a president has to work with members of Congress and foreign leaders repeatedly over the course of years. Governing is about relationships much more than it is about transactions.

All of which suggests that Trump may want to reform some of his ways. He is picking a good many fights in a job where it is smart to bank goodwill. President George H.W. Bush frequently picked up the phone and called leaders around the world. Telephone diplomacy was a good way of staying current, but even more it was a good way to develop trust. That way, when Bush needed to ask for something — as he did after Saddam Hussein’s 1990 invasion of Kuwait — he was much more likely to get it.

A president should sometimes resist the temptation to drive for the best deal possible. Trump writes in his book that “I aim very high, and then I just keep pushing and pushing and pushing to get what I’m after.” This makes great sense in isolated transactions, but, again, few interactions in politics tend to be isolated. It is important to leave enough on the table so the person on the other side can sell the deal back home. Everyone in politics has politics. The alternative is likely to be no deal or one that unravels.

It is also wise to leave something on the table for another reason: It may be necessary to deal with that same person or government down the road on a different issue. Indeed, the future is likely to be one in which countries are both competitive and cooperative. Pushing too hard in one situation may preclude working together when it is important to do so. Trump should keep this in mind with respect to his damaged relationship with the president of Mexico.

It is important not to threaten or bluff unless you mean it. The biggest error of Barack Obama’s presidency arguably occurred after he warned Syria’s President Bashar al-Assad that he would face dire consequences if he used chemical weapons. But when Assad crossed this red line — repeatedly — he paid no direct price. The result emboldened him, sapped his opponents’ confidence and raised questions worldwide about whether Washington could be taken at its word. Allies everywhere questioned whether the United States would be there for them in a crunch.

Similar considerations argue for fidelity to the truth. Trump suggests that, in real estate, a little hyperbole — what he describes as “truthful hyperbole” — never hurts. It will, however, hurt him in his current job. The day will come when this president will need others to take him at his word in justifying a particular response to a threat that cannot be proven beyond all doubt. Alliance ties, as well as the ability to deter foes, will depend on it. The bottom line is clear: There is little or no place for exaggeration in the Oval Office, much less for alternative facts.

It is essential, too, to understand who has more at stake before laying down a challenge. Trump blundered early on when he threatened to abandon the one-China policy. He wrongly judged that he could derive leverage; predictably, though, there was no give in China’s position on an issue its leaders judge as existential. As a result, it was Trump who was forced to back down if he wanted Chinese cooperation on other issues, such as doing something about North Korea’s nuclear and missile programs.

Like it or not, politics and geopolitics alike are all about the art of relationships.