Justin Theroux says being kind is the secret to a happy marriage.

Jennifer Aniston and Justin Theroux

Jennifer Aniston and Justin Theroux

The 'Girl on the Train' actor wed Jennifer Aniston last year and believes being nice and caring towards each other is a necessity.

He told People magazine: "Being kind, that's it. I think that's the best one. Approach each situation with kindness."

The 45-year-old star has also admitted that respecting each other helps couples stay together.

He revealed: "There's no such thing as a perfect couple, but there are couples that can be good together.

"We appreciate each other's sense of humour, we respect one another, and we get along. It sounds simple, but it's true."

Justin recently revealed how being married to 47-year-old Jennifer had had a calming effect on him.

He said: "Obviously. I'm married.

"I think marriage taught me to settle a little bit. It does have a calming effect.

"I think it's at what age you make that commitment. When you hear about people in the '50s getting married at 20, you're like, What were they thinking? My grandparents were together for over 50 years.

"My grandfather used to write one sentence every day in his journal: 'I love Anne more than ever today.' I think that was his meditation - keeping him in his marriage, and also his appreciation for it. It was very touching."