“I think it’s about being committed to each other, about having the same values and wanting the same things from life,” Roberts told Britain’s HELLO! magazine, reports femalefirst.co.uk.
“As for keeping it going through the years, a girlfriend who has been married for a very long time said a great thing once.
“She said, ‘If you want to be in an interesting relationship, stay in the same one’ and I think that’s true because 15 years into our relationship, I find the continual excavation of what goes on between us quite fascinating. So maybe the real key is to stay invested and interested in your partner,” she added.
The “Money Monster” actress, who has children Hazel and Phinnaeus, 10, and Henry, 8, turned 48 last month.
That she’s still young at heart resonates in the fact that she celebrated her special day by playing mah-jong.
“I celebrated (my birthday) wildly by having a free day where I didn’t have to do anything but stay in my house and have fun, which I did from the moment I opened my eyes until I fell asleep on the couch, blissfully exhausted.
“I played about 15 rounds of mah-jong with my girlfriends and had a really nice day.”