Reggie love, personal assistant to US President Barack Obama for four years, is leaving the White House to focus on his studies.
Speaking to ESPN, he said the president is "like big brother to me".
Before working at the White House, Mr love played on Duke University's basketball team.
As personal assistant, known as the president's "body man", the 30-year-old has performed roles as varied as personal valet, gatekeeper and basketball partner.
"His ability to juggle so many responsibilities with so little sleep has been an inspiration to watch," Mr Obama said about Mr love in a statement. "He is the master of what he does."
Mr love joined Mr Obama's office in 2006, when the future president was a fresh-faced senator from Illinois.
Since then they have been virtually inseparable.
ABC News estimated that Mr love and Mr Obama have travelled 880,780 miles (1.4 million km) together since the beginning of the 2008 presidential campaign.
The close relationship even extends to the bathroom, with Mr love often in attendance when the president flosses（牙线） his teeth.
"If he had it his way, I think he'd floss in private," Mr love said. "I think the fact that he was comfortable with me is probably a product of, you know, he's beaten down. I've been around for so long."
Mr love, who will leave the White House before the end of the year, revealed he had asked Mr Obama about his view before making it final.
"I said, 'Mr President, I just wanted to get your advice and your opinion on this. I'm thinking that maybe I need to spend more time focusing on school and taking some time off of here,'" he said.
"And he was very supportive of it."