The 44-year-old actress, who is married to cameraman Danny Moder, said she always feels better about her looks when she is happy with her personal life, reported Femalefirst.
"I think optimism and having a sense of humour definitely help but happiness is something you cultivate. Once you find it, that's the key to looking beautiful.
While Roberts is feted for her looks, she says it takes a lot of work to to make her look like a movie star.
"I don't wake up with some sense of fabulosity. I'm perfectly aware of how many people it takes to put this movie star appearance on. I'm a regular person doing an extraordinary job," she said.
The "Pretty Woman " star also said she does not understand why people opt for cosmetic surgery.
"With today's science, people have become crazy with trying to move their face around, it's bizarre," she added.
