From the White House to the Vatican, Schwarzman's plainspoken advice is in high demand.
"When the two parents are fighting, all the children, the other countries, they get scared and they start not having normal economies," he told Inside Edition. "And if the two parents really break apart, everyone will be a loser."
But how did the son of a shopkeeper from Philadelphia become the confidant of heads of state? It started on Wall Street — badly.
"I was the most junior person in the room and [one of my higher-ups] started screaming at me that I wasn't sitting up straight and what was I doing at this meeting?" Schwarzman recalled.
"I had never been attacked before, let alone by a powerful person," he continued. "I just sat there in stunned amazement."
And yet, the moment taught him a valuable lesson. "Fifty years later, if there's an important meeting, I am on the edge of my chair and my back is completely straight," Schwarzman said. "What seems to be some kind of disaster taught me to behave differently."
It's one of the many lessons Schwarzman shares in "What It Takes," along with the story of building a business with a staggering $545 billion under management.
That also started badly, he confided. Every potential investor said no. But that's OK, he said, because it's all about anticipating what can go wrong and heading it off at the pass.
"You have to be a little delusional at the beginning," he said. "You look at every major decision from the perspective of not what goes right but what goes wrong, what can hurt this? What can turn victory into defeat? I spend most of my times thinking about what those risks are, what bad things that could happen that will stop us from being successful. "
Another tip? Don't wait, timing is everything.
"When you can get something done, don't dilly-dally around," he said. "Opportunities aren't there very long. When you see one that's terrific, you jump on it."
Nowadays, Schwarzman is giving back, creating his own scholarship inspired by the Rhodes Scholarships, called the Schwarzman Scholars. The program aims to help elite students study in China, which leads to another bit of wisdom from Schwarzman.
"Find people who can teach you things and let them help you," he said. "Everybody needs to be helped."