Shayne Higson still vividly remembers the trauma of watching her 77-year-old mother succumb to multiple brain tumours.
"She didn't want to suffer at the end stage," Ms Higson told AAP.
"But there was nothing her doctor could do to treat her, and it was also not legal to assist someone's death."
Ms Higson and her sister also were forced to stand by as life-loving Jan Ryder asked for help to end her "torture" in November 2012.
"The last five days were so traumatic," she said.
"I knew then and there I would work to change the law."
That 11-year journey will end on Tuesday as Ms Higson's state of NSW becomes the sixth and last state in Australia to enact voluntary assisted dying.
Eligible adults must have an incurable and advanced terminal illness that will likely kill them within six months - or 12 months for those with neurodegenerative conditions.
Requests for lethal medication must be made by the affected person, be enduring and go through a doctor specifically authorised to accept requests.
About 600 to 900 terminally ill people are expected to take up the option in the first 12 months.
Ms Higson, the chief executive of Dying With Dignity NSW, said having the power available would comfort so many more.
"We know from interstate it gives people a great peace of mind that they have a choice," she said.
"Most people are under palliative care and it's not a choice between the two - voluntary assisted dying is a last-resort option."
Had the power been available and taken up by Ms Ryder in 2012, it might have brought her death on 15 days earlier, providing an "enormous difference" to her and her extended family, Ms Higson said.
The laws also provide solace to long-time lung cancer sufferer Janet Cohen who sought provisional approval to end her life in Switzerland in 2020.
"It's about regaining a sense of control and autonomy," she said.
"Having this option has given me back some feeling of agency and now I can die in Australia ... I can now have my loved ones around me and go on my terms."
Ms Cohen and Ms Higson will join other campaigners at state parliament on Tuesday for a celebration of sorts, marking the new laws while recalling friends and family who passed too soon to use them.
The ACT and the Northern Territory remain the only jurisdictions without voluntary assisted dying.
A Howard government-era ban on the procedure in Commonwealth territories was lifted last year, enabling the ACT to begin developing its own laws.
Voluntary assisted dying does not enjoy universal support, however.
Christian Voice Australia, currently helmed by a former director of Fred Nile's Christian Democrat Party, said the new NSW law was "an outrageous attack on the sanctity of human life" pushed by "anti-life lobbyists".
"No amount of euthanasia safeguards will protect against abuse," Greg Bondar said.
