United Kingdom, Jan. 24 -- Leighton Meester considers "just liking each other" to be key to relationship success.

The 39-year-old star has been married to actor Adam Brody since 2014, and Leighton admits that their relationship success is actually built on some fairly simple ideas.

The actress - who got engaged to Adam back in November 2013 - told People: "It's so funny, because the other night somebody asked me that, and I was like, 'I wish I had the answer,' [but] I think just liking each other, and getting along is a big part of it.

"It is sort of at a base level what it's about. Just being like, 'I really like this person.'"

Leighton also thinks it's important to "always be open and willing to work on yourself" in a relationship....