A retired nurse from London who travelled to Switzerland to end her life disliked the "indignity" of ageing, her partner has said.
Gill Pharaoh, 75, was apparently healthy when she made the decision to go to the Lifecircle clinic in Basel.
Campaigners against assisted dying have described the case as "chilling".
But her partner John Southall told the BBC: "Choosing the time you die is a human right."
Ms Pharaoh wrote in a blog published by the Sunday Times: "I feel my life is complete and I am ready to die."
She said while she was largely healthy, an attack of shingles five years ago and tinnitus had made it difficult to take part in the activities she had once enjoyed.
She wrote: "I am not just whinging. Neither am I depressed. Day by day I am enjoying my life.
"I simply do not want to follow this natural deterioration through to the last stage when I may be requiring a lot of help."
Care Not Killing, a group which campaigns against assisted dying, condemned Ms Pharaoh's case as "deeply troubling".
A spokesman said: "It sends out a chilling message about how society values and looks after elderly people in the UK.
"It seeks the introduction of death on demand for those who fear becoming a burden, even if they are otherwise fit and healthy."
Her partner, John Southall, told BBC London he had put a lot of questions to her over the years about her intention to get help to take her own life, but said he saw it as "her decision".
He added: "It was not for me to feel confident [in her decision], but I did agree with the rationale and the logic".
He explained that in her career as a palliative care nurse she had seen "a lot of people in pretty miserable circumstances - it gave her a dislike of the indignity of that".
He added: "Choosing the time you die is a human right, who should deny us that?"
A 2014 study by Zurich University suggested an average of around one person a fortnight travels from the UK to Switzerland to receive help to take their own life.