Nicky Hilton Reveals Her Marriage Rules with Husband James Rothschild — and How Their Kids Play a Part (Exclusive)

Nicky Hilton is sharing the secrets to her successful marriage.

On Saturday, Oct. 5, the fashion designer, 41, spoke exclusively with PEOPLE about her longtime relationship with her husband James Rothschild , whom she married in 2015, at the MyTheresa launch party for her holiday collection with Rebecca Vallance in Los Angeles.

Nicky credits her parents, Kathy and Richard Hilton — "who've been married for over 30 years " – for being an "amazing template" for a successful relationship.

"I feel like some of the advice my mom has always given me is [to] never stop having fun, never go to bed angry and just to stop and smell the roses and enjoy every moment," Nicky says.

When it comes to her and Rothschild's marriage rules, she adds, "My husband and I, with our work, we travel a lot, but we always try ... We will not leave the children alone. So we try and divvy up our work trips and make sure that we're always present."

The couple shares three children — daughters Lily-Grace Victoria , 8, and Theodora "Teddy" Marilyn , 6, and son Chasen , 2.

As for when Nicky and Rothschild, 39, have time for just the two of them, she says, "We always try and just make that special alone-time date night."

Saturday's star-studded event saw the attendance of Nicky's parents, her sister Paris Hilton and her husband Carter Reum , Kris Jenner, Rachel Zoe , Jennifer Tilly , Kelly Osbourne and Dylan Mulvaney .

Speaking about her collaboration with Vallance, Nicky tells PEOPLE, "I have been a huge fan of Rebecca's designs for many years. [I've] been wearing them. Me, my mom, my sister — we all love them. So to be able to collaborate with one of my favorite designers is really a dream come true. We have such a similar aesthetic, DNA, and I think you will see that in all the pieces."

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To pull together the limited-edition collection which, according to the website , "features impeccably cut statement dresses that capture the iconic Rebecca Vallance brand codes, reimagined through Hilton's lens," Nicky and Vallance were in "constant contact" via Zoom and in person.

"She would fly to New York, we would meet in Europe, and we really, really worked very collaboratively on this collection," Nicky explains of their working relationship.

The collection is said to tap into "that special holiday feel through a timeless color palette," which Nicky says includes some unexpected hues.