Oprah's interview with Diaz, 43, will air this Sunday at 9 p.m. on OWN

By Nicole Weisensee Egan
October 24, 2016 03:31 PM

“In an interview airing Sunday night, Brittany Maynard‘s widower Dan Diaz tells Oprah Winfrey that keeping his promise to get right-to-die legislation passed is helping him cope with the loss of his wife.

“I’m not one that does well just sitting around,” Diaz said on Oprah: Where Are They Now after the talk-show host asked him if he’d given himself time to grieve.

“The one thing that does keep me going is working toward fulfilling the promise I made to her,” he said in the interview, which was taped Feb. 5.

“Brittany wanted to see legislation [passed] in all states, really, but in California in particular so that people wouldn’t have to go through what we did,” he says in the interview.

On Oct. 6, Maynard, 29, launched an online video campaign with Compassion & Choices, calling for nationwide access to “death with dignity” laws.

Last June, she and her family moved from California to Oregon to gain access to the state’s Death with Dignity Act.

Dan Diaz and Brittany Maynard
Courtesy Brittany Maynard

Maynard, 29, was terminally ill with brain cancer and ended her own life with medication prescribed by her doctor on Nov. 1.

However, Maynard was well aware that most terminally ill people aren’t in a position to move to another state as she did, which is why Compassion & Choices released a call to action from her on Nov. 19 on what would have been her 30th birthday.

Since then, 15 states plus Washington, D.C., have introduced right-to-die legislation, and more than 50,000 people have sent letters urging their state lawmakers to pass the bills in her honor, according to Compassion & Choices.

On March 25, the California state senate health committee will hold a hearing on the legislation. Debbie Ziegler, Maynard’s mother, will testify and Diaz will speak at a news conference beforehand.

Former LAPD narcotics sergeant and attorney Christy O’Donnell, 46, who is suffering from lung cancer that has spread to her brain, will testify as well.

O’Donnell can’t move to Oregon like Maynard did because she does not want to uproot her daughter, Bailey Donorovich, 20, who is a college sophomore and works full time at a local pet store.

So if change doesn t come in time for her, she will likely die the way it’s been described to her – by drowning in her own fluids from the lung cancer.

“I won’t break the law,” she tells PEOPLE in a story on newsstands Friday. “I’ve spent my entire career upholding it. It’s an injustice I can’t die the way I want to.”

Catch the full interview with Diaz on March 15 at 9 p.m. ET on OWN.