The 33-year-old dancer from Caerphilly said she had "cried all morning" before ringing the bell marking the end of her chemotherapy treatment.
Amy Dowden has said she feels "lucky and grateful" to ring a bell in hospital - marking her final chemotherapy session.
The Strictly Come Dancing star was diagnosed with grade three breast cancer earlier this year.
The 33-year-old dancer from Caerphilly in south Wales has made occasional appearances throughout the current series, but was not partnered with a celebrity as she underwent treatment.
Ahead of her eighth and final session of chemotherapy, which she started in July, Dowden told her Instagram followers she had "cried all morning".
But after the session, she said: "This day of ringing the chemo bell felt like an endless distance away and at points, I thought I'd never make it. I'm so proud of myself."
Described as her "toughest journey yet", Dowden said the treatment "hopefully has now given me the chance of more life" which she is "eternally grateful for".
Alongside an emotional video on Instagram, the dancer said: "I'll never be the same Amy again but, what I do know is I'm so much stronger than I ever knew, and I have made the most amazing friends along the way.
"I hate looking in the mirror at the moment, but I know this is a small price to pay and 'this too shall pass'."
Dowden initially underwent a mastectomy and daily hormone injections to retrieve her eggs. In August, she revealed she had contracted sepsis after her first round of chemotherapy.
The dancer said that she now awaits an MRI to determine if she needs more surgery.
Amy Dowden arriving at the red carpet launch of Strictly Come Dancing 2019, held at BBC TV Centre in London, UK.
In the clip, amid tears, she hugged and thanked the staff at the unit that had looked after her during treatments.
Several Strictly stars sent Dowden their well wishes, including fellow dancer Dianne Buswell who said it made her "so happy".
Former contestant Michelle Visage wrote: "We love you, Amy."
And Dowden, who married fellow professional dancer Ben Jones in July last year, said her dancing shoes were "warming up" and that she "can't wait to get back in the training room".
She joined the series in 2017 and has since partnered celebrities including actor Danny John-Jules, James Bye from EastEnders and McFly's Tom Fletcher.
Chemotherapy is a treatment where cancer cells are killed using medicine.
It stops cancer cells reproducing so they don't grow and spread in the body, according to the NHS website.
Side effects include feeling tired, sick and hair loss.
Dowden received praise from viewers for recently reading Strictly's terms and privacy notice without a wig.
