BOSTON -- Long-distance running has been called the "loneliest sport." Not for Rebekah Gregory, a survivor of the 2013 Boston Marathon bombing. On Monday she took her thousands of social media followers along with her during this year's running of the race.

"I have two choices: I can be mad that this happened to me, or I can be blessed that I have a daily reminder that life is short and I am still here," said Gregory.

Rebekah Gregory runs the last three miles of the 2015 Boston Marathon CBS News

Gregory and her son Noah, who was 5 at the time, were both injured when the first bomb went off. She decided last November to have her damaged leg amputated, but not before a tongue-in-cheek goodbye to her limb.

"Go get yourself one last pedicure on me...and enjoy it because tomorrow I will be cutting you out of my life for good," Gregory wrote on Facebook.

"I made the decision to amputate my leg purely based on the fact that I was on pain medication every four hours," said Gregory. "I was totally immobile, I was in a wheelchair for the majority of the time, and that was not okay with me."

The 27-year-old single mother has been training to run on her new prosthetic leg at her home in Texas.

"It is the best decision I have ever made for myself," said Gregory. "I am doing normal things again. I took my son to the movies the other day. I walk through the airport and I don't have to use a wheelchair. And if I am in jeans nobody can even tell that I have a prosthetic leg."

Gregory was determined to run the whole marathon, but last week her doctors told her she wasn't ready. They told her she would be doing more damage to herself and end up back in surgery.

"I had to compromise, which I am not very good at doing sometimes," said Gregory.

That compromise was to run only the last three miles, but the nature of a marathon is not just the distance run, it's the defeat of an enormous personal challenge.

"This is the hardest thing I've ever had to do," said Gregory. "When I crossed the finish line, I got my life back today."

It's a finish line that's given her a new beginning.