On a chilly winter night at the tip of New York’s Long Island, Julianne Moore celebrated her 60th birthday with her husband, Bart Freundlich, and their two children. “She was happy it was just the four of them,” a friend confides to Closer Weekly exclusively, on newsstands now. “She really is happier than she’s ever been.”

The arrival of a milestone birthday didn’t rattle Julianne. “It’s not about staying young. It’s about being alive,” she insists. “Because we have a limited time on earth, let’s try to stay engaged in our lives until we die. That’s it. That’s all we’ve got.”

In fact, as the years have passed, Julianne’s life has only become sweeter. She began acting professionally shortly after her graduation from Boston University in 1983 but didn’t hit her stride as a leading lady until her late 30s — which is quite rare in Hollywood.

“Oh my God. I’ve been talking about aging since I was 30,” she says with a chuckle. Playing complicated roles earned Julianne four Oscar nominations before she finally took home the Best Actress prize for her portrayal of a woman being treated for Alzheimer’s in 2014’s Still Alice when she was 54.

Likewise, the happiest chapters in Julianne’s personal life arrived later. She met her husband Bart, 50, in 1996 on the set of The Myth of Fingerprints, which he directed. “It was pretty unexpected,” admits Julianne, who had been married once before. But “it’s true — that thing about love growing. It does and it gets way better.”

Who Is Julianne Moore's Husband

The couple, who have two children, Caleb, 23, and Liv, 18, often work together and recently adopted a Lab-mix rescue pup they named Hope. “They love to watch movies and play games. They are not drama-filled people,” says the friend. “They sometimes disagree, of course, but they are generally on the same page.” This summer, Julianne and Bart marked their 17th wedding anniversary. “I think that’s what’s been nice about it. It doesn’t feel like a long time,” says the actress.

Julianne believes that everyone should celebrate their years instead of mourning the passing of time. “We’re all aging — children are aging,” she says. “That’s what life is, and we have to accept that there’s a beginning, a middle and an end. It’s important to remember that there’s a time frame, so we can be awake for it.”

That perhaps is the greatest lesson: People who worry too much about the years passing risk squandering whatever time they have left. “Enjoy it! It’s a privilege to age. You could be dead,” reasons Julianne. “I think it’s really important to be where you are.”

— Reporting by Rick Egusquiza

For more on this story, pick up the latest issue of Closer magazine, on newsstands now.