They've been together for 11 years, married for just over four, have two kids and are generally seen as one of Hollywood's most solid couple - but as Kristen Bell will tell you, even her marriage to fellow actor Dax Shepard requires a lot of work.

The actress shared a handwritten note that she had given to a friend who was also getting married, and decided to share it on Twitter for the day that was in it yesterday.

"I was writing a note 2 friends who were getting hitched," she said. "I wrote congratulations then thought "Kristen! Arent u old & married? Dont u have any wisdome to share?!" When i was done, I realized Id written the A-Z of what keeps my marriage w/@daxshepard1 healthy."

See her commandments for keeping a marriage strong below: