"In a way it was a relief for me, but it was still bloody sad and a shock. I miss her terribly but she wanted me to be happy, and that is what I will now try to focus on."
The Herald on Sunday reported last year that De Houwer had sought out ways to end her own life, despite her incapacity, because she did not want her husband held culpable.
"She has to do it herself, because if I help I'm looking at 14 years' jail," he told the paper. "I'd much rather be there and hold her hand. It's bloody awful," he said.
De Houwer's diagnosis was rare: one of only 68 in the world in the past half-century, doctors told the couple.
She had spoken publicly of a "peaceful pill" bringing numbness within seconds, and death within minutes, that she hoped to source from overseas - but Grant said it was not needed in the end.
This week, Grant told the Herald on Sunday he had put his wife to bed about 10.30pm, after she complained of having a headache.
"I went to bed about midnight and when I woke at about half past six, she was gone."
Her body was cremated. Last Sunday, a moving service for close friends and neighbours was held at the couple's home.
"We were able to show a documentary that was made in 2000 about Belgians who had left their country because they had fallen in love," Grant said.
"We were filmed for a week and it is a nice love story that showed Yoka as such a happy, positive person."
The couple, who founded the successful Tasman Bay Herbs business in the mid-1990s, were members of the Nelson chapter of the voluntary euthanasia group Exit International.
They went public with their story to bring attention to the issue.
"When Yoka found an appropriate exit plan it was very empowering for her," Grant explained. "She didn't want to go to the meetings any more and we concentrated on the time we had left."
He added: "If she had carried out her plan I could not have helped her do it, because if I had I could be facing up to 14 years in jail."
Grant said he would continue to press the Government to make progress on an "end of life choice" private member's bill, championed by Nelson-based Labour list MP Maryan Street.
The bill would make it legal for those diagnosed as terminally ill and in full control of their mental faculties to choose to die, and for assisting clinicians or family members to be protected from liability.
"About 22 people die from cancer every day in New Zealand," Grant said.
"Some die nicely but others wish they had a choice, and I will continue to support a euthanasia bill."
Yoka was originally from Belgium.
A family service will be held there for her on April 6, and her ashes will be scattered both here and in her former homeland.