While his best bud Ben Affleck is in the midst of a tough divorce, Matt Damon is gearing up to celebrate his 10th wedding anniversary with wife Luciana in December. Though the couple have been together for over a decade, Damon says he "wouldn’t give anybody any advice" about maintaining a successful relationship.

"I think marriage is insane," Damon admitted to ET. "It's a crazy idea but I love being married to my wife. So I wouldn't tell anybody else about their relationship. But I'm lucky I found my wife. And I guess maybe, if there's any secret … it's to feel lucky."

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ET caught up with the actor at the junket for his latest film The Martian, where he confessed that there’s no hard and fast rule to staying together in the spotlight.

"So much of it is out of your hands," Damon said. "I mean, I just had that conversation with my father this weekend. He says the same thing to me. Says it's God's grace, is what he said. Because you just don't get lucky."

Damon and Affleck, who won their first Oscars for Good Will Hunting, have been good friends since childhood, and the Boston-bred boys celebrated an interesting milestone on Aug. 15, when the Red Sox won for the first time on Affleck’s birthday since the release of their Oscar-winning film.

"I was in Boston with my family actually. It was kind of a meaningless, it was 43 you know? It wasn't that big," Damon joked of his friend’s big day. "I think he was actually in Atlanta with his family. So we missed each other but...he’s good. He’s good."

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Damon also had a laugh about staying in shape for The Martian, in which he plays an astronaut who gets stranded on Mars, and the upcoming fifth Bourne Identity movie.

"I always look for an excuse to hang out and have a beer and a burger," he joked. "But no, right now, I have to be in shape, just until February, and then I'm going off the rails."

The Martian hits theaters on Oct. 2. Watch the new trailer for the film below.

And be sure to tune into Entertainment Tonight on Wednesday for more with Matt Damon! 

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