What you're missing is that there's a huge difference between toughing it out during "training" and toughing it out during "events". In training, absolutely. I

What you're missing is that there's a huge difference between toughing it out during "training" and toughing it out during "events". In training, absolutely. If something doesn't feel right, back off, let your body recover. But during events? Whether it's the big through-hike or that marathon or the ironman, you need the ability to push past the pain and suffering, and learn that your body is better than you think at fixing itself. It's effectively impossible to injure yourself in a permanent way, I promise you. Few marathon runners will run a full marathon during training, even at slower paces. Before I ran my first one, the longest training run I ever did was about 35km, with most runs below 25 (for comparison, a marathon is 42.2km). The sheer amount of suffering you'll endure during those last 7.2km is probably the worst you'll ever feel in your life, but slowing to a walk or dropping out at that point is ridiculous. Like the author said, having the mental fortitude to tough it out when the going gets tough is what separates athletes from wannabes -- and knowing the difference between "this is just a training run" and "this is the event I've been preparing for over the last 12 months" is key.