Michael Douglas has learned over the years to let some comments slide. 

The 76-year-old Oscar-winner was recently mistaken for his 18-year-old daughter's grandfather at her high school graduation and the star didn't let the remark cut him too deep. 

Douglas recalled the experience while appearing Monday on "The Kelly Clarkson Show." 

"I gotta tell you Kelly, it's a little rough when you're going out the doors and the other parents are saying, 'Oh congratulations…you must be so proud of your granddaughter,'" he admitted. 

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"I said, 'Well, I don't know man. Yeah okay,'" Douglas remembered. "I'm not gonna take it personal, they're just trying to be nice."

"The Kominsky Method" actor called the day "wonderful" regardless. "I'm so proud of her," he said of Carys.

(L-R) Michael Douglas, daughter Carys Zeta Douglas, and wife Catherine Zeta-Jones. (Dimitrios Kambouris/Getty Images for Michael Kors)

Douglas shares Carys and son, Dylan, 20, with his wife actress Catherine Zeta-Jones, 51. Douglas is also a father to son Cameron, 42, from his previous marriage to Diandra Luker. 

Now, with both kids gone, the pair are empty nesters.

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"It's scary. It really is," Douglas admitted on the TODAY show in May. "You look at each other and go, 'Well, it's just you and me babe.' "

"You forget how many conversations you sort of hide behind in terms of talking about your kids and what's going on next and this and that, and then one day you just look at each other," he reasoned. "We're 20 years now, so all those good years of paying attention to each other are paying off now."

Douglas and Zeta-Jones married in 2000. She told People magazine in July that they won't be celebrating the milestone with any big party this year. 

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"Not that I'm a big party fan anyway," she said. "It would be nice to get all our friends together in one space, but we're not doing that until we're completely out of the woods. So I will raise my mask and let my husband passionately kiss me, then I will put it firmly back on."