“I asked him whether he’d seen a certain article, and he said: ‘No, send it my way. I’m looking for something to read right now,’ ” said a close friend who asked not to be identified discussing Mr. Petraeus’s private life. “He kept such a grueling schedule. This is unchartered territory for him right now.”

Another friend, who also asked not to be named, had similar thoughts. “Several of us are concerned,” the friend said. “He’s a very active individual. He needs to stay active.”

Mr. Petraeus’s friends say his first priority is to make things right with Holly Petraeus, his wife of 38 years, and their two grown children, but Mrs. Petraeus has not been keeping her husband company at home during the day. A spokeswoman for the federal Consumer Financial Protection Bureau, where she works, said on Wednesday that Mrs. Petraeus has been at the office every day since the scandal broke…

“The way he describes it, he said, ‘You know, I wasn’t sure right away that she was writing a biography; I thought it was a book on Afghanistan,’ ” said one of the friends, referring to Ms. Broadwell’s decision to turn her unfinished dissertation into a book on Mr. Petraeus. The friend did not explain how Mr. Petraeus could have had such a view. “It sort of developed over time, and he realized belatedly that it was about him.”