After tough training runs, when 2 miles felt like 20, Nancy Eaton worried she wouldn’t finish this year’s Boston Marathon. Not even come close. To push past the fatigue and the doubts, she imagined conversations with her close friend Amanda Turner Russell.

Eaton would tell Russell, “Look what you got me into.’’ The always-exuberant Russell inevitably answered, “You can do it! You got this!’’

Finishing the Boston Marathon was not Eaton’s dream, at least not this year. It was Russell’s.

While the two labor and delivery nurses shared a love of distance running and traveled together to races across the country, Russell, 32, could not coax Eaton into applying for a charity number. Barely recovered from two broken bones in her left foot, Eaton, 55, planned to cheer on Russell this time and qualify down the road.

Then, in December, everything changed.

Two days before Christmas, Russell left her Hanover home for a training run. While going down Winter Street in Hanson, a car swerved across the road and slammed into her. The impact left Russell with traumatic head and neck injuries. While doctors tried to save Russell’s life, her mother, Sally Turner, “knew almost immediately that she wasn’t coming back.’’

At her daughter’s hospital bedside, Turner asked Eaton, “Would you run Boston for Amanda?’’ Without hesitation, Eaton replied, “Yes, I’d be honored to.’’

“I knew the marathon was one of Amanda’s bucket list things,’’ Turner said. “I knew Amanda loved Nancy and Nancy loved Amanda. I knew nothing would keep Nancy from the finish. A lot of people volunteered to run for Amanda, but I wanted Nancy to do it.’’

Eaton committed to the marathon, even though she knew training would be emotionally and physically painful. And it was. Almost every run brought back memories of Russell. The night shifts they worked together at Beth Israel Deaconess Medical Center. The costumes Russell planned for every race. The music concerts they attended.

On Monday, nearly four months after Russell’s death, Eaton hopes a marathon finish will offer some small measure of closure for family and friends.

“She was like another daughter to me,’’ said Eaton, who raised six children in York, Maine. “There was a huge age difference, but running, being single moms, being huge Disney fans bonded us. With the race getting closer, it’s been very emotional. I think I’ll start out [the marathon] fine, but then I don’t know. I’m going to channel Amanda in. She’s just going to have to run with me.’’

Shared sunrise

When Eaton and the other night shift labor and delivery nurses see the sun rise at BIDMC, they often feel Russell is there with them. Russell would sneak onto the hospital’s roof and snap photos of the new day dawning and share them with coworkers. And if Eaton was on vacation, Russell sent along that day’s sunrise photo with the message, “This one is for you.’’

That was typical Russell — always thinking of others, bringing people together, and making friends smile with gestures big and small.

When she needed to pick a charity, Russell chose Beth Israel’s Neonatal Intensive Care Unit because, as Eaton said, “when a baby comes out and it’s not doing what it’s supposed to do, the NICU is a godsend.’’ More than $22,000 in NICU donations have been pledged on Russell’s still-active fundraising page. And Eaton added that Russell “would have been floored by that number.’’

When she traveled, Russell would buy souvenirs not only for her fellow nurses, but also for their children. When Eaton mentioned she dreamed of someday opening a whoopie pie bakery called “The Big Whoop,’’ Russell designed T-shirts for it. When one 12-hour shift after another after another after another left the nurses exhausted, Russell cheerily reminded everyone, “It’ll be fine by Sunday.’’ Now, “Fine by Sunday’’ has become the motto of the BIDMC labor and delivery department.

And Russell never lost her optimism or love for her job, even when she handled the toughest cases: the babies who don’t make it.

“She was very passionate about taking care of patients who experienced loss,’’ Eaton said. “When patients came in and there wasn’t a heartbeat or something happened with the baby, she took care of those patients. There are people who shy away from those patients and she always said, ‘I’ll do it. I’ll take them.’?’’

Part of that care is assembling a memory box with handprints and footprints and a lock of hair if the baby was far enough along. Whenever Eaton had a tough time with the handprints, she asked Russell for help. A year after patients suffer a loss, the labor and delivery nurses mail them a “Thinking of You’’ card. Now, those cards feature sunrise photos taken by Russell.

“No one else could do this for Amanda the way Nancy could,’’ said Annie Chatfield, who is part of the close-knit group of labor and delivery nurses at BIDMC. “It’s a sense of one of our own doing it for Amanda. It’s very cathartic for the unit, for all of us, to know that Nancy is doing it for Amanda. It feels right. It brings us one step closer to healing.’’

Running with wings

When Russell applied to run the marathon with Team BIDMC, she wrote, “It wasn’t until coming to Labor and Delivery that I got into running, with the inspiration of my coworker Nancy Eaton.’’ It was Eaton who convinced Russell to race distances longer than 5K. And when they started running events together, it was Eaton who would move back to a slower corral so she could start beside Russell — consideration that Russell soon rebuffed from her more competitive colleague.

“She knew me well enough that, after we’d run a couple times together, she was like, ‘You just need to go up there. Get out of here,’?’’ said Eaton, laughing at the memory.

When Russell raced, it was for the personal challenge, camaraderie, and costumes, not fast times. She once ran a 5K dressed as Buzz Lightyear, and persuaded Eaton to ditch her usual T-shirt and shorts for slightly more elaborate race-day getups. For a Disney race a couple years ago, Russell made herself and Eaton blue butterfly wings. They completed blue-and-yellow, Boston Strong-themed race outfits.

Eaton still has her wings. On Monday, she hopes one of Russell’s friends will be able to hand her the wings around Mile 25 so she can cross the finish line wearing them.

There will be plenty of Russell’s family and friends along the course. The BIDMC labor and delivery nurses will be there, some in the crowd and some as race volunteers. Russell’s mother, younger sister Katie, and 8-year-old son Gavin plan to be at the finish line waiting for Eaton some four hours after she starts.

When Eaton crosses the finish line, Turner believes it will feel as if her daughter was completing the race, too.

“Amanda is still with us in spirit,’’ Turner said. “She always will be. I know there are an awful lot of us out there who miss her. I’ve discovered I have a whole new family now, all the people who loved her are now part of my family. Nancy is part of my family.’’

At this point, Turner became emotional, collected herself, then added, “Everybody is trying to find their way forward.’’

BY SHIRA SPRINGER | GLOBE STAFF

Shira Springer can be reached at springer@globe.com. Follow her on Twitter @ShiraSpringer