Kristen Bell and Dax Shepard have couples therapy.

Dax Shepard and Kristen Bell

Dax Shepard and Kristen Bell

The 'Frozen' star believes attending the sessions makes their marriage stronger and thinks it is the secret to their great relationship.

She said: "We have a very healthy marriage and we got there by doing therapy when we needed it, and constantly doing fierce moral inventories.

"We both take responsibility when we are wrong, and I think it is easy to work with him because I married him, because I enjoy spending time with him and I trust him. That is exactly what I want in someone that I work with."

Just like any other couple, Kristen and Dax - who have daughters, Delta, two, and Lincoln, three - have fought in the past and she recalled a particular incident in their first year of dating when they rowed over what songs to put on a music playlist.

She added to People magazine: "We were fighting about the first year of our relationship because it's a power struggle, and we were fighting about the playlist, and I got so mad at him at one point that I refused to hold onto him. So I was on the back and just held onto the [bike] because I didn't want to touch him."

Meanwhile, Kristen previously revealed the couple are "very focused" on making their marriage work.

She shared: "One thing I like to reiterate ... is that we've done a lot of work on our relationship. We're very focused on staying together. We've made a choice to love each other but realise relationships are a lot of work. I think it's responsible to be honest about that.

"It's hard work, working out the kinks of how learning how to argue because we disagree on almost every topic on the planet. We earned our relationship, which we're very proud of. We're the Paula Abdul video 'Opposites Attract' personified. I thought I had this life thing down pat when I met Dax. I didn't realise that I needed a much bigger toolbox to have confrontations and disagreements with people ... You do better in the gym with a trainer; you don't figure out how to cook without reading a recipe. Therapy is not something to be embarrassed about."