Peter Sarsgaard and Maggie Gyllenhaal are, in fact, the real thing.

And after more than 14 years of marriage, the Memory actor chalks up his long-lasting relationship with the actress to one basic rule.

“Tell the truth,” Peter told E! News’ Francesca Amiker in an exclusive interview. “Isn’t that all there is? It’s pretty simple. It’s not that complicated. Isn’t that the secret to any friendship or relationship?”

For Peter—who shares kids Ramona, 17, and Gloria, 11, with Maggie—honesty is, indeed, always the best policy.

“Otherwise, even if it’s a nice lie, even if it’s a lie to prop someone up or help them avoid what they’re trying to avoid, you’re not living in reality,” he continued. “And that’s the only place to live in.”

And these days, they’re living in—and relishing—the holidays and their annual traditions.

“There’s a church that we go to that has a midnight mass that I don’t go to any other time throughout the year,” the 52-year-old, a close friend of Maggie’s brother Jake Gyllenhaal, explained. “The midnight mass there is extraordinary, and Maggie and I are sometimes able to sing.”