Grace Smith says she was able to give up alcohol, but that quitting smoking seemed impossible.
Back in 2011, the then 25-year-old had a stressful fundraising job in New York.
"I didn't have any healthy coping mechanisms," she says. "One of the ways that I was coping with all the stress and anxiety was through partying.
"I was living in the Lower East Side, and that's what all my friends did too - we worked really hard all day long, and we partied really hard all night. It took a real toll on me, physically and mentally."
She says that she was able to quit nicotine after just the one hypnotherapy session. And the experience inspired her to become a hypnotherapist herself.
Today Grace runs her business Grace Space Hypnosis, which is said to offer online hypnotherapy sessions to more than 250,000 people around the world, including the bosses of Fortune 500 companies, athletes and celebrities.