"I didn't think I would be walking this path again and certainly not this soon. But I'm just so overwhelmed by the support, the prayers, the love, and it's really sustaining me," she told ABC11 in an exclusive interview at the GMA studios in New York.
Robin got the news from doctors that she has something called myelodysplastic syndrome - or MDS - on the very day she and her Good Morning America colleagues were celebrating their first ratings victory over the Today show in 16 years.
Doctors told her they think it's a result of her breast cancer treatment. MDS is a malignant disorder of the bone marrow, and she'll need a bone marrow transplant.
"I'm still kind of like in this 'is this happening again?' and the bone marrow is up and coming, the transplant. It's gonna be difficult. But I'm very confident that things are gonna go very well and I'm very blessed that my sister is such a great match," said Robin.
Robin's sister Sally Ann - a local news anchor in New Orleans - is a perfect match.
"Because of my sister, it significantly increases my chances for this being a cure," said Robin.
Last week, ABC News held a daylong marrow donor drive to help people who need a transplant and do not have a perfect match like Robin. With a simple mouth swab, 200 people joined the world's largest marrow donor registry.
So the silver lining in Robin's illness is how many others may be helped.
"What did my mom say the first time: 'Make your mess your message,' and our message here is: If you can, if you're able to be a donor, there's approximately 6,000 people a day who go online looking for a donor," said Robin.
More than 70 percent of people who need marrow donors are not as lucky as Robin. They do not have a perfect match, and they turn to a national network of potential donors.
"We're educating people that it's just a simple swab, and if you're selected, often times, it's like a blood transfusion. It's not the big needles and thinking about how painful and all that, but to know that you can save someone's life is priceless," said Robin.
Robin said - as she undergoes treatment - she's having some tough days, and she finds inspiration from the late Kay Yow - the legendary NC State women's basketball coach who lost a valiant battle with cancer. Coach Yow told Robin during her first cancer fight to "swish her feet in bed," because then you'll want to get out of bed and start moving.
Watching her on your TV at home, you'd never know Robin is having any tough days. The only sign she's having treatment is the bandage on her arm.
"There are these little tubes right here and so it's very easy for them to draw blood and to administer whatever drugs they need to. And I keep it nice and hidden and your viewers there in the Triangle are never the wiser. But I'm trying to do a little fashion statement," Robin explained.
When Robin's bone marrow is ready, she'll have the bone marrow transplant. Her doctors think that'll be in the fall. She'll need to be away from work for a number of months while her bone marrow recovers.
If you would like to become a bone marrow donor - go to bethematch.org.
Since Robin announced her diagnosis, online donor registration has increased 10 times - to about 4,000 a day. Robin's doctors say her prognosis is excellent.