Though she's been married to Jordan Bratman for nearly five years, Christina Aguilera says not much has changed since she first began dating the music exec in 2002.
"Marriage unites you and makes you official, but it didn't change our relationship. All the things like wanting to work hard and play hard -- they were always important to us," she tells the October issue of Cosmopolitan UK. "We've been married for five years now, and I think the secret is in always keeping it interesting. You have to make time for yourselves."
So how does Aguilera let her man know she cares?
"I leave little lipstick marks on the bathroom mirror for when he wakes up, and little notes written in lipstick on the mirror and in the shower," she says. "Little notes, little cards, little 'I love yous' here and there, just to keep things fun and alive."
Still, the "Not Myself Tonight" singer admits that even the most loving marriages require effort -- and a lot of patience.
"It's important to be open to growing together, and when the going gets tough, you have to see how you can make your relationship more special and how you can spend more quality time together," Aguilera says. "Everyone has rough patches, everybody grows and we all change. It's important to give each other room to grow and to accept them for who they are."
These days, Bratman isn't the only man in Aguilera's life. Since giving birth to her son Max in 2008, the 29-year-old singer admits that motherhood has helped strengthen her relationship with her husband.
"Having Max has brought us closer together," she says. "[Jordan] changed the first nappy while I was in bed recovering from my C-section -- and he's been so hands-on ever since. When I see them together it makes my heart sing and melt at the same time."