I'm hoping this goes somewhere eventually, but I have a half-formed thought that I need to express.
If you improve a race time, you think that whatever you changed since the previous race is the reason you improved. Beside non-training reasons, improvement might have been from a long-term trend, rather than an immediate cause.
When you improve, you think that repeating the change that led to improvement will lead to further improvement. The unique circumstances before your improvement will never happen again. Doing something again does not guarantee the same results, nor is more of something necessarily better; there might be something else that is better still.
If you make a change and improve, then make the same change and fail to improve, you might think "I've become accustomed to the stimulus. I need even more of it."
Success leads to more. Failure leads to more. More leads to injury.