Leighton Meester considers "just liking each other" to be key to relationship success

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.

She explained: "I think being with another person and knowing that they're going to be imperfect and challenge you, and that you are far from perfect, is [important]."

Meanwhile, Leighton recently opened up about her "journey of self-love".

The actress explained how she's learned to cope with her critics over the years.

Leighton told People: "I think self-love, for me, does look like just speaking positively to myself.

"Certainly speaking positively of others too, but [it's important] that I really include myself in that, because there are plenty of not-so-nice feelings that you can absorb out from the world. But I really do have to enjoy continuing the journey of self-love and telling myself and believing that I'm worthy of it, just because I exist."

Despite this, Leighton acknowledged that her journey of self-love hasn't always been easy.

The actress - who is, perhaps, best known for playing Blair Waldorf in the hit TV series Gossip Girl between 2007 and 2012 - shared: "There was a long time where I was like, this is kind of embarrassing to say and feel, and really put weight onto."