People.com reports that Affleck told Playboy magazine recently that Garner helped provide him with a stable family life, which kept him away from a string of unsuccessful films and from being fodder for gossip following his relationship with Jennifer Lopez.
"Getting to know her, falling in love with her and being connected with her gave me a foundation to reach out and say, 'Okay, I'm going to do Hollywoodland. I'm going to direct 'Gone Baby Gone'," Affleck said.
The couple married in 2005. They have three children - son Samuel, 21 months, and daughters Violet, seven-and-half, and Seraphina, four-and-half.
Affleck says Garner "is by leaps and bounds the most important person to me in that respect".
"Over the past 10 years she has allowed me to have a stable home life while accomplishing my professional goals. Once I'd made it, the most critical thing was that she said, 'If you're going to work 24 hours a day, that's cool. I'm going to be here'."
"That allowed me to think, Okay, that's what I'm going to do. I'm going to kill myself over this next period of time."