She added: "The world is a beautiful place, travel has been my greatest teacher, my close friends and folks are the greatest givers. I even have a ring of support around my bed as I type.
"Goodbye world. Spread good energy. Pay it forward!"
Ms Maynard was diagnosed with stage IV glioblastoma multiforme, an aggressive form of terminal brain cancer and in April doctors gave her just six months to live.
She then made headlines around the world after announcing she intended to die under Oregon's Death with Dignity Act.
"But it will come, because I feel myself getting sicker. It's happening each week."
The newlywed recently managed to tick visiting the Grand Canyon off her bucket list after previously announcing that it was one place she hoped to visit before she died.
Brittany Maynard and her husband Dan Diaz pose at the Grand Canyon National Park in Arizona. Photo / TheBrittanyFund.org/AP
Last week she had revealed on her website that she had managed to travel from her home in Oregon to Arizona with her husband, mother and stepfather "thanks to the kindness of Americans around the country who came forward to make my 'bucket list' dream come true".
In her latest statement, a video produced by end-of-life choice advocacy group Compassion & Choices, she acknowledges that some people have been skeptical about her story.
"When people criticise me for not waiting longer, or, you know, whatever they've decided is best for me, it hurts," she said, "because really, I risk it every day, every day that I wake up".
Maynard also revealed that her health has been deteriorating and described a recent "terrifying" day when she had two seizures and found herself unable to say her husband's name.
"I think sometimes people look at me and they think, 'well you don't look as sick as you say you are,' which hurts to hear, because when I'm having a seizure and I can't speak afterwards, I certainly feel as sick as I am," she said.
Maynard had previously said that she planned to take the medication she'd been prescribed on November 1 because she wanted to celebrate her husband's birthday on October 30.
Read more:
• Terminally ill US woman delays her death-date
"The worst thing that could happen to me is that I wait too long because I'm trying to seize each day,' she said, "but I somehow have my autonomy taken away from me by my disease because of the nature of my cancer."
After her recent visit to the Grand Canyon, Maynard had written on her website in glowing terms about the experience.
"The Canyon was breathtakingly beautiful, and I was able to enjoy my time with the two things I love most: my family and nature," she wrote.
Images taken at the Canyon show her kissing her husband, Dan, and embracing her mother and stepfather, grins across their faces.
But just a day after the experience, she suffered her "worst seizure thus far", which left her temporarily paralysed and tired for the rest of the day.
"The seizure was a harsh reminder that my symptoms continue to worsen as the tumor runs its course," she wrote.
She finished the post by saying she found meaning in her battle for other states to implement right-to-die laws, as Oregon and four other state already have.
"My dream is that every terminally ill American has access to the choice to die on their own terms with dignity," she wrote. "Please take an active role to make this a reality."
Brittany Maynard, left, hugs her mother Debbie Ziegler next to a helicopter at the Grand Canyon National Park. Photo / TheBrittanyFund.org/AP
Ms Maynard gained nationwide attention after she shared a heart-wrenching video that explained why she was choosing to end her life at age 29 - while campaigning to expand right-to-die laws.
She explained that, after suffering intense headaches, she was diagnosed with a brain tumor in January and was initially given 10 years to live, which she said was devastating.
But in a scan a few months later, doctors told her the cancer had progressed to Glioblastoma multiforme - an aggressive tumor.
Sufferers have a life expectancy of around 14 months.
When she learned that she would die painfully and slowly, she decided to move from her home in California to Oregon, which has a 'Death with Dignity Act'.
After releasing her video, critics lambasted her as selfish, but in an interview with CBS she said she was suffered immense pain - and wished she didn't have to be making the decision.
Maynard said her biggest regret is that she will never get to have a family.
"I'd say most of my sadness centers around how much I wanted a family," Ms Maynard told CBS This Morning.
"And it feels like for me, that was always, like, how you created a legacy was, like, through your children. And sort of inadvertently - through sharing my story, I've realised there's a bit of the legacy I'm creating this way and I'm not ashamed of that. I'm not ashamed to attach my name to what I think is a right that should belong to all terminally ill Americans."
"I don't want to die," Ms Maynard explained. "If anyone wants to hand me, like, a magical cure and save my life so that I can have children with my husband, you know, I will take them up on it."
She also has made a deal with her mother, Debbie, that if she travels to Machu Pichu in Peru after her passing, Brittany's spirit will meet her up there among the breathtaking Inca ruins.
In the same interview, Debbie, who raised Ms Maynard on her own, talks about the discussion she had about her daughter when she learned of her decision.
"Early on, I told her, 'It would be my honor to take care of you, whichever way; if you need to be fed or diapered, it would be my honor,'" she said.
"And that was important for me, for her to know."
Ms Maynard's husband, Dan Diaz, also spoke about how sad he is that he will not get to spend the rest of his life with the woman he married little over a year ago.
"That was the original plan, right?" he said. "But the reality that, I guess, that feeds into the argument of quality of life versus just quantity."
Brittany's final statement
Goodbye to all my dear friends and family that I love.
Today is the day I have chosen to pass away with dignity in the face of my terminal illness, this terrible brain cancer that has taken so much from me ... but would have taken so much more.'
She added: 'The world is a beautiful place, travel has been my greatest teacher, my close friends and folks are the greatest givers. I even have a ring of support around my bed as I type.
Goodbye world. Spread good energy. Pay it forward!
Where to get help:
• Lifeline: 0800 543 354 (available 24/7)
• Suicide Crisis Helpline: 0508 828 865 (0508 TAUTOKO) (available 24/7)
• Youth services: (06) 3555 906
• Youthline: 0800 376 633
• Kidsline: 0800 543 754 (4pm to 6pm weekdays)
• Whatsup: 0800 942 8787 (1pm to 11pm)
• The Word
• Depression helpline: 0800 111 757 (available 24/7)
• Rainbow Youth: (09) 376 4155
• CASPER Suicide Prevention
If it is an emergency and you feel like you or someone else is at risk, call 111.
- Daily Mail
