Kristin Cavallari keeps the "spark alive" with her husband by always missing each other when they're apart.

Kristin Cavallari

Kristin Cavallari

The former 'The Hills' star has been married to American football quarterback Jay Cutler since 2013 and believes the key to their successful marriage is always wanting to be around each other.

She told E!'s Daily Pop: "I have always said: it's kind of nice to miss each other. I think that's how we've always kind of kept our spark alive.

"Jay just signed with the Miami Dolphins, so he's in Florida. Some days it's crazy and I can't wait for bedtime and other days I'm like, 'Okay, it's actually not that bad.'"

Meanwhile, Kristin - who has Camden, five, Jaxon, three, and Saylor, 21 months, with Jay - has put a "lot of work" into her relationship.

She said: "Honestly, I think communication and it's so much easier said than done. I know that Jay and I have to make a conscious effort. You have to put in work for a relationship. You can't just get complacent and lazy. You have to still value and appreciate the other person. I think that when you don't that's probably when you start to get in trouble. And, I mean, we have our issues. Our relationship isn't perfect. But we love each other and we work on it and we make a conscious choice to work on the relationship and I think that that's what you just have to do.

"God, I'll be the first to admit it - especially with three little kids! It's hard. You have to make time for each other and try to get out of routine here and there. It's much easier said than done. It really is difficult sometimes. We have a lot of great tools that we learned from therapy and I think that was the most beneficial part. Just learning how to communicate and walking away with some great tools, which we'll always be able to use."