The 35-year-old, who could leave Stamford Bridge on a free transfer this summer, has been engaged to the Northern Irish broadcaster since 2011.
"People say opposites attract, but when you live together, you need to be harmonious, and she's my best friend," Lampard told Red magazine.
"She's made me content. That sounds soppy, but I've been very happy since I've been with her. Our personalities are very similar.
"I've got a lot of respect for what she says – she's sharp. I bounce my problems off her, and I'd like to think I help her with her stuff too."
Lampard is father to daughters Luna, eight, and seven-year-old Isla from a previous relationship with Spanish model Elen Rivas.