Entertainment Movies Justin Theroux on His No. 1 Rule for Marriage with Jennifer Aniston: 'Approach Each Situation with Kindness' Justin Theroux reveals what makes his marriage with Jennifer Aniston work By Jodi Guglielmi Jodi Guglielmi Instagram Twitter Writer-Reporter, PEOPLE People Editorial Guidelines Updated on October 5, 2016 06:19 PM Share Tweet Pin Email Photo: Ari Perilstein/Getty Life definitely isn’t imitating art for Justin Theroux. The actor may play a man in a twisted and failed marriage in his upcoming movie The Girl on the Train, but in real life, he couldn’t be happier with his relationship with wife Jennifer Aniston. Theroux, 45, opened up to PEOPLE about his marriage, admitting that the secret to their love boils down to one simple philosophy. “Being kind, that’s it,” he says. “I think that’s the best one. Approach each situation with kindness.” The Girl on the Train, which is based on Paula Hawkins’ best-selling novel, follows Rachel (Emily Blunt), a heavy drinker who is obsessed with a couple she sees out of the window on her morning train ride to work. When the woman, who happens to be the family nanny of Rachel’s ex-husband Tom (Theroux), shockingly goes missing, Blunt’s character finds herself entangled in the investigation. During his chat with PEOPLE Now, Theroux also teases the film and reveals just how excited he was to work with his “good friend” Blunt . The Girl on the Train hits theaters Oct. 7.