The top runners who lean heavily on gadgets like a GPS system are the exceptions. Most elites have their courses, assign a distance to each, and leave it at that. They’re secure enough in their running that they don’t need the constant external feedback from a Garmin or similar gadget. They know that what matters on a run is achieving a certain effort for a certain duration. Most of the time they base that on the signals they’re getting from their bodies, not from a potentially faulty device on their wrist.
Granted, it can be nice occasionally to know exactly how far you ran at what pace. GPS units are great if you’re doing something like a long run with the last several miles at your goal marathon race pace. That’s valuable feedback about your progress toward a specific goal that combines the elements of time and distance.
But too many runners overrely on their measuring gadgets during normal runs, when it’s not important to hit specific combinations of time and distance. To them, a run is successful only if the gadget spits out the right numbers. It’s worth making this point again: A mile has no meaning to the human body. You’re imposing artificial definitions of success on your running by letting a device that speaks only in those measurements tell you if you had a good run. Learn to distinguish between information about your running that has merit and information about your running that’s just information for the sake of information. Learn to interpret and be guided by the signals from your body about proper effort levels.