Ahhhh, Fall! Cooler temps, warm blankets, pumpkin-spice everything, and marathons. Some of the most notable races of the year are coming up in the next couple of months and you can bet there will be a few first-timers. Fitness training app, Freeletics asked its 15 million users what they wish they had known before they ran their first marathon. Let us know what you think and if you think these tip...