The CEO of Goldman Sachs reveals one of the hardest parts about his job that he never saw coming

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David Solomon may have been groomed for his role as CEO of Goldman Sachs, but there was one downside that still came as a surprise to him.

"I've counseled CEOs for a long time and have had a lot of CEOs talk to me about what it feels like to be a CEO, and you feel a little bit lonely and a little isolated, and information flows are different. I thought I understood that. When you sit in the seat, it's really different," he said in a " Squawk Box " interview from the World Economic Forum in Davos, Switzerland.

Solomon officially took over the top job from Lloyd Blankfein on Oct. 1.

He's since been grappling with the deepening international scandal in which Goldman bankers were accused of helping a Malaysian financier steal billions of dollars from an investment fund called 1MDB. Last week, Solomon apologized to the Malaysian people for the role of one of his former bankers, Tim Leissner, in the scandal. Leissner pleaded guilty to bribery charges in August.

Those difficulties aside, Solomon told CNBC he's "incredibly optimistic" about the firm. His biggest "upside surprise" since ascending to CEO has been the reaction of the Goldman staff.

"I knew this was a great organization. I knew we had great people. I knew we had great opportunities. But when suddenly you step into the position of leading the organization and you can feel the organization really rallying behind the direction that you want to go, that's endorsing," he said.

Solomon is no stranger to the employees of Goldman. He rose his way through the ranks of the investment bank and served as Goldman's president and chief operating officer before becoming CEO. He's also a disc jockey in his spare time.

Now that he's in the top spot, time management has become even more crucial, Solomon said. He spends about one-third of his time focusing on strategy, one-third on people and one-third on clients, he said. However, that can change based on what else comes his way.

In fact, Solomon said one of the hardest things for business leaders is to know what to say "yes" to and what to say "no" to when things are thrown at you.

"You've got to be better at saying 'no' to things that aren't really relevant for your core mission or what you're really trying to accomplish for the organization," he said.

— CNBC's Hugh Son contributed to this report.

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