"My mother still believes in Santa Claus. We tried to break it to her once, but she wasn't having it," the actor, 30, tells GQ in its January issue, on newsstands Dec. 21.
Donna Gosling, who accompanied Ryan to the Oscars when he was first nominated in 2007, has a rare gift, says her son. "There are very few believers in the world, but my mother is one of them. I don't know if she'd admit that this is why she does it, but it's just more fun to believe in Santa than not to."
If the Blue Valentine actor, who's been linked to actress Blake Lively of late, sees the value of nurturing the fantasy, he's also about keeping it real – which explains why he got a job at a deli after starring in the Hollywood hit The Notebook.
"I'd never had a real job," he says – which is a problem, he adds, for many in Hollywood. "They have meals. They go to Pilates. But it's not enough. So they do drugs. If everybody had a pile of rocks in their backyard and spent every day moving them from one side of the yard to the other, it would be a much happier place."
And he tries to remain grounded amid a life he never expected.
"Look, this is crazy," he says. "I don't understand how I'm here, living this life, wearing this suit. I assume I'm going to pay for it someday … And that's okay. It seems fair to me. I just want to be ready for it. I want to meet it like a gentleman."