A 56-year-old woman is planning to run her 41st marathon next month. Here's what she does when she doesn't feel like training.

• Find your motivation to exercise by setting small goals, a marathon runner says.
• She started by walking and has since finished 40 marathons over three decades.

Getting into a workout routine, and a healthier lifestyle, starts with the first step — literally.

One of the best ways to stay motivated to exercise is to focus on small, attainable goals, even if it's just putting your shoes on and walking out the door, according to a runner who will be completing her 41st marathon next month.

Aubrey Barr, 56, of Massachusetts said she never thought of herself as an athlete, having grown up with severe health issues after a diagnosis of acute lymphoblastic leukemia at age four.

But in college, she developed a running habit that helped her feel mentally and physically strong, eventually prompting her to take on the Boston Marathon, her first, in 1992. From there, the habit just stuck.

"No one sets out to do a marathon and thinks 'one down, 39 more to go,'" she told Insider. "It was so organic, I didn't even know it was happening.

She'll be running in the New York City Marathon on November 5th for the charity organization Fred's Team, for which she has raised $500,000 toward cancer research since the organization's debut in 1995.

Barr said the secret to staying motivated to exercise is listening to her body, finding a community of runners, and taking each day and each run a step at a time.

Start with short, light workouts and build up over time

Barr never consciously decided to start running, let alone tackle long distance. It all began with a simple walk. While in college, Barr said she had taken to following a nearby trail to "blow off steam," but noticed the five-mile loop took a while to finish and thought jogging a bit could help her save time.

"I didn't think of myself as a runner, I just thought 'I need to scoot a little bit and pick up the pace,'" she said. "I just progressed to walking briskly, then would give myself little goals."

Her gradual approach to running is backed by exercise science experts and running coaches, too. One of the biggest mistakes people make with running is doing too much, too fast — workouts should feel easy and not leave you sore, Boston Running Center coach and exercise physiologist Joe McConkey previously told Insider.

Barr said that while taking on an exercise goal like a race can be intimidating, it doesn't have to be hard on your body if you focus on steady progress over time.

"When you layer on the miles gently and give yourself a chance to recover properly, it works," she said.

Don't obsess over data

Today's exercise enthusiasts have more options than ever when it comes to high-tech ways to track progress and optimize performance, but a simpler approach to running can sometimes be better, according to Barr.

While she used to strive to beat her previous time, she said making peace with her own pace has helped her keep a lasting love of running, and prevents a workout from feeling like a chore.

"When I got to the point where certain times were slipping away from me, I would feel kind of down. If the watch is giving you such grief, don't wear it," Barr said.

Find a workout buddy

Barr said another factor that kept her hooked on running for decades was the community she's found, including through the New York Road Runners.

"It is all about the human connection, hearing about mistakes you made while training, victories you've experienced, angst you're feeling before your first marathon. I'm grateful for the Road Runners for a great experience," she said.

Phoning a friend to hit the trail or gym is also a science-backed way to stick to your exercise plan, a Harvard researcher previously told Insider.

Prioritize what you enjoy about exercise

One hard truth about exercise, especially endurance training, is that there will always be moments when you feel tired or unmotivated, but finishing the workout can pay off, Barr said.

Her personal strategy is to remind herself of the feelings of joy and accomplishment that come during or after a run, instead of dwelling on the sense of fatigue or sluggishness of the moment.

"The first time you push through doubt and do it anyway is a conscious effort. But then you feel grateful and know it will be worth it," Barr said. "It's about knowing what a gift it is to have a healthy body and move around."

Listen to your body

Barr said a simple strategy for staying motivated is to start with just three minutes of exercise or 20 steps, which feels like a comfortably easy goal to achieve. If she's still tired by the end, she'll take a rest day instead of whatever workout was planned.

But the vast majority of the time, Barr said that those three minutes fly by and she feels ready to finish a full workout. However, she's also mindful that not every successful workout has to be maximum effort

"It's the getting started that's the hardest part, but once I do, I'm grateful, even if it's a slow run," she said.

In fact, research suggests that up to 80% of running workouts should be done at an easy pace, since slow, steady exercise can help build endurance and speed, triathlete and exercise specialist Dr. Morgan Busko previously told Insider.

Barr said she often adjusts her workouts to keep runs shorter or slower if that feels right for her body, and it's helped her prevent injury and burnout over decades of running.

"You need to know your life circumstances. Sometimes there are just days and weeks when you can't log all those miles so make the miles you can run count," she said. "I think if people just trust their instincts, they'll be really pleased with the results."