"I was 18 when we first met, 19 when we first started dating," the 27-year-old said in the issue that hits newsstands November 18. "I really don't believe that you will love the same thing when you're 20 as you do at 30. So that was my rule: Before the age of 25, I would never get married."
The singer explained that she wanted to get to know herself first before making the commitment to the hip-hop mogul, which she finally did in a secret ceremony in New York this past April. Now they have become each other's support system.
Jay, 38, offers up advice for his wife all the time, B added, revealing the best wisdom he's shared with her so far: "I guess probably that we're all human," she said.
"I don't care if you're picture-perfect on every magazine cover, and you're the most handsome, successful, coolest guy — you still get sad, and you still get your feelings hurt, and you still get confused and vulnerable and nervous and scared. You have to find a person you can make it through the tough times with."
Beyoncé, whose double album I Am ... Sasha Fierce drops next Tuesday (November 18), also admitted that when it comes to criticism, she is her own worst enemy. "I feel like I'm my own competition," she said. "I don't try to compete with other people. I just try to better myself."
B revealed one of her secrets to staying on top of her game: studying videos of herself in great detail, like an athlete. "I go and watch everything that I've done," she said. "I have my YouTube days, when I watch every performance, and I listen to my music, and I watch my videos to figure out what I need to do, what I need to fix and how to become a better singer."