Then, the day before this interview was to take place, he was hit with a bombshell. Vanity Fair magazine published an interview with Ms. Garner, in which she discussed the dissolution of their relationship. Speaking of Mr. Affleck, she told the magazine: “I always say, ‘When his sun shines on you, you feel it.’ But when the sun is shining elsewhere, it’s cold. He can cast quite a shadow.”

In person, Mr. Affleck was friendly and funny, but also soft-spoken and vulnerable. At times he seemed anxious and out of sorts, as if waiting for some other shoe to drop.

Despite vowing not to, he did eventually address Ms. Garner’s Vanity Fair profile.

And though he said he could not pinpoint why he chose to play Batman right now, he did offer a broader theory on the parts that currently appeal to him.

When he watches other movies that strain to make their protagonists likable and valorous, Mr. Affleck said: “I find that boring. Instead, I think it’s interesting how we manage the best version of ourselves, despite our flaws and our weaknesses and our sometime tendencies to do the wrong thing.”

He has also realized that for all of his Hollywood success, some part of him will always feel like a relentless striver who must prove, through his work, that he has a right to be there.

“That never goes away,” he said. “All these habits that we develop, that help us at some point, they have flip sides. In this case, it’s hard to turn that feeling off.”