Agile focuses on painful things with the goal of making them less painful. The blog post compares embracing the pain of exercise to the Agile practice of taking big painful jobs, like merging and releasing, and streamlining them so you can do them more often in smaller increments. The pain decreases because of automation, practice, and reduced change size. Basically, the complexity of tackling change scales more than linearly with the size of change, so splitting a large change into smaller changes means less pain if the constant factor of handling each change can be made small. From this perspective, Agile means tackling change in small chunks, and Agile practices are focused on reducing the constant factor. The end result is less pain for the same amount of forward progress.
The reason I don't buy the analogy is because embracing the pain of exercising doesn't reduce the pain and doesn't have anything to do with the size or frequency of workouts. It's entirely about perception. You know the pain is there, but your experience of the pain changes. It's like your brain learns the pattern exertion => accomplishment => pleasure and satisfaction and short-circuits the logic so that exertion is rewarded directly with pleasure and satisfaction. Or maybe it's endorphins. Whatever the explanation, pleasure is layered over the pain, but the pain remains underneath. It's still there, but it doesn't hurt. Or it hurts, but it feels good. I don't know how to describe it, but the physical sensation of pain is still there.
I disagree specifically, and also with your interpretation of his point.
Embracing the pain of exercise absolutely does reduce the pain. If you don't exercise for months, it hurts like hell to get started again. The natural reaction, especially for people who have never exercised, is to avoid the pain and stop. But if you are returning to exercise after, say, an illness, you will slowly work through the pain until your body responds. There is still some underlying pain, but it is much less for a person who's in shape.
But I don't think he's making the direct analogy you're seeing. I think his broad point is exactly what the title says, that one should lean into the pain in many aspects of life. Exercise and software development are just two examples of applying the principle.
The reason I don't buy the analogy is because embracing the pain of exercising doesn't reduce the pain and doesn't have anything to do with the size or frequency of workouts. It's entirely about perception. You know the pain is there, but your experience of the pain changes. It's like your brain learns the pattern exertion => accomplishment => pleasure and satisfaction and short-circuits the logic so that exertion is rewarded directly with pleasure and satisfaction. Or maybe it's endorphins. Whatever the explanation, pleasure is layered over the pain, but the pain remains underneath. It's still there, but it doesn't hurt. Or it hurts, but it feels good. I don't know how to describe it, but the physical sensation of pain is still there.