Nowhere is the saying “life is what happens to you when you’re busy making other plans” more true than in endurance sports. For a race like a half-marathon or marathon, you often need to sign up several months in advance just to secure your spot.

Over those next few months of training (oh, and that little thing called life), myriad obstacles can get in your way, from big projects at work to injury. But figuring out when you should take a DNS (did not start), or even a DNF (did not finish) can be a tough call to make — one that pro runner Ryan Hall made at last week’s L.A. Marathon, as he felt his lead slipping. When emotions ride high and intuition goes out the window, hear what our running experts have to say on whether you should — or shouldn’t — toe the line.

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If You’re Injured

Runners are notorious for being a little creaky around the edges from the miles of wear and tear they put on their body. It’s not uncommon to experience some degree of pain or soreness through the course of a training cycle. “But if the pain is increasing as you run or if it’s at a moderate to severe level before you begin the run,” says Michael Conlon, the owner of Finish Line Physical Therapy, “then it’s worth paying attention to.” He recommends choosing a pain-free form of cross-training, such as biking or swimming, or running on an Alter-G Anti-Gravity Treadmill if you have access to one.

If you’re training for a longer race, like a half-marathon or marathon, you should be even more wary about pushing through injury. “I’m overly cautious and would recommend a runner not run the race if an injury is casting doubt on their ability to finish, run without pain, or otherwise have an enjoyable experience,” says Jason Fitzgerald, a USA Track & Field certified coach and the founder of Strength Running.

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You can look to see if your race offers options to defer until the next year or transfer your bib to someone else. If you still have friends or family competing in the race, you may want to go cheer them on — which is fine if that’s what you’re really there to do. “If you’re just there to torture yourself,” says licensed clinical and sports psychologist Bhrett McCabe, PhD, then don’t do it. “It’s nice to see a race from the other perspective, so make sure you have a purpose if you’re going.”

If You Need to Take a DNF

“My calves were cramping, but it was more fatigue than injury. I still regret today that I dropped out.”

A DNF is always a very tough decision, says Fitzgerald, “especially as most runners love finishing races for the pride, camaraderie and potentially a nice medal. But it’s a good idea to stop and quit the race if a pain surfaces or persists that is sharp, stabbing, or otherwise very intense.” It’s likely you could cause additional damage by pushing through, further aggravating the injury, or creating new ones.

Michele Gonzalez made the call during the Staten Island Half Marathon last year that she’d need to drop out. Her calf had cramped up at mile nine, and her stride changed in order for her to keep running. For her, “Finishing a tune-up race was not the goal,” she says. “It was to get 13.1 miles of hard, fast running and to practice pushing when things got tough.” She decided to drop out because she believes no race is worth a serious injury.

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She also took a DNF at the New Jersey Marathon last year, due to issues with nerves, fueling and hydration. It was a goal race for Gonzalez, who dropped out when she realized she wouldn’t hit the time she was aiming for. Making the call wasn’t clear-cut, though. “You need to differentiate between hitting the wall and having something actually hurt,” she says. “My calves were cramping, but it was more fatigue than injury. I still regret today that I dropped out.”

If You’re Undertrained

Of course, sometimes the problems present themselves much earlier than race day. It happens: You’re signed up for the marathon, but it’s just not in the cards. Life somehow got in the way, and there’s no chance you can run 26.2 miles in one shot. But if you’re lucky, your event might have other options like a half-marathon, 10-mile race or 5K.

“Some athletes might decide to drop down to a shorter race,” says Dr. Amanda Visek, a sports psychologist at George Washington University. If you’ve made this decision far enough out, you can reduce your mileage and adjust your training for the new distance. She also recommends accepting and embracing the new race goal and then doing whatever is necessary in terms of mental or physical preparation to meet your goal.

If You’re Not Ready to Race

“Take into consideration all of the variables at that moment — your training, conditioning, your next race — and begin to formulate a plan.”

We know, we know — the Type A part of you doesn’t want to hear this. But if you can still comfortably finish the distance, just not at a racing pace, you can always turn it into a more relaxed run. And sometimes, says McCabe, you will surprise yourself and run better than you could have hoped for.

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“Expectations are entitlements, so they raise pressure and limit the ability to compete naturally,” McCabe says. “They force you to read into each experience and evaluate how you are performing compared to your desires.” Instead, he encourages his athletes to make “demands” of themselves during the race, such as “I know today will be difficult, but I am going to work to stay in the moment rather than worry about the future.”

There’s also the option of shifting your focus to help others. If you have a friend who’s doing the race, maybe that means pacing them to a PR (if their fast pace is a more comfortable pace for you), an experience that can be nearly as rewarding as hitting your own personal best. Or, if you’re really dead-set on just running for fun, turn the race into a game. How many pictures can you take? How many high fives can you get?

Find Your Next Goal Race

Whether you’ve skipped the race altogether or dropped down in distance or pace, you might be itching for your next adventure.

“As soon as someone drops out of a race, they can immediately begin to adjust their goal or begin a new goal for a different race,” says Visek. “Take into consideration all of the variables at that moment — your training, conditioning, your next race — and begin to formulate a plan,” says Visek.

But don’t rush in prematurely. McCabe suggests waiting several days so that you’re not registering based on an emotional reaction. Take some time to process what happened leading up to your dropping out or down.

However, if you’re avoiding racing out of fear, it’s important to get back out there sooner rather than later. “We know from anxiety research that the more we avoid [something], the stronger the fear is,” McCabe says. “The longer you try to steer clear of this adversity, the worse the fear will become, so face it head on.”

You’ll know from your physical and mental training when you’re ready for your next race.

Have you ever had to drop out of a race? Tell us about it in the comments below.

Originally posted May 30, 2014. Updated March 2015.