With her girlish good looks and spunky charm, it’s hard to believe Sandra Bullock will turn 55 on July 26 — even for her. “After a while, you have no idea how old you are because you’ve lied so many times,” she quips.

As she marks the milestone birthday, Sandra has many reasons to be thankful. Most important are her son Louis, 9, and daughter Laila, 7. “I finally realize, Oh, this is what I was supposed to do when I grew up,” Sandra says. “Not to be an actress — to be a mom. This is my purpose.”

Getting to this moment of clarity hasn’t always been easy. Sandra endured a painful, public divorce from ex-husband Jesse James (who admitted to infidelity) in 2010. “My life took a trajectory that wasn’t very pleasant,” she says. “But I feel like it had to happen in order for me to fully understand what family was about.”

Bryan Randall and Sandra Bullock with their new dog

Adopting Louis and Laila as a single mom changed Sandra’s perspective on life. “No one understands the shift in priorities about having a child in your life until you have a child in your life,” she says. “Everything is about them being OK, being in school, having what they need, their moments. I need to be there for every single moment they have.”

In 2015, Sandra met photographer Bryan Randall, 53, when she hired him to take pictures at Louis’ birthday party. They’ve been inseparable ever since, and her kids approve of the relationship. “He’s super kind, and for the kids, he’s sort of No. 1,” says Sandra. “And I’m No. 2, but I get it because he’s more fun and has better treats.”

Still, Sandra is hesitant to wed again, having been burned once before. “She wants to marry Bryan, especially now that Louis and Laila are asking more questions about it, but it’s going so well that she doesn’t want to jinx it,” an insider exclusively tells Closer Weekly in the magazine’s latest issue, on newsstands now. “Sandra is definitely gun-shy about walking down the aisle again, and who can blame her?”

In fact, the fiercely independent Sandra has never been a big fan of marriage. “My mother always told me, ‘Don’t get married. Make your own life. You don’t need a man,'” recalls Sandra, whose mother, an opera singer, died at 58 in 2000.

Her father, who served in the Army during World War II, passed away last year at 93, and the loss hit Sandra hard. “Life, I realized, happens whether you schedule it or not,” she says. “That just blew my mind.” Luckily, she had loved ones to lean on. “The people who got her through that dark time were Bryan and her kids,” the insider says.

At an age when actresses have traditionally found it hard to land leading roles, Sandra has kept her career in good shape, starring in the hit heist flick Ocean’s 8 and the buzzy Netflix chiller Bird Box (which she also produced) last year. Yet she plans to focus less on acting, especially if it means being away from home. “I don’t leave that much, and I don’t work that much anymore, either,” she says. “I don’t know if I always want to be in front of the camera. I love producing. I love the camaraderie, the adventures and the stress.”

Bryan Randall with Sandra Bullock and kids

Having survived both personal and professional ups and downs over the years has given Sandra a sense of balance. “Everything works out the way the universe wants it to work out,” notes the actress, who won a best actress Oscar for The Blind Side and a worst actress Razzie for All About Steve in the same year. “It makes sure you don’t get a head that’s too big. I love it.”

Sandra considers herself lucky to have led the life she’s lived. “If I die tomorrow, will I have gotten everything in the world I’ve ever wanted? No,” she says. “But I will have gotten everything that’s made me happiest.”

Adds the insider, “The most important lesson she’s learned is that family comes first. A simple night at home making dinner is when she’s happiest. She already has it all.”

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