I think of rationality in instrumental terms too. The point is achieving your ends most reliably and most efficiently, and rationality broadly construed is the way to accomplish those ends.

I gave the example of being overly attached to material trinkets, not just being attached. Being overly attached by definition could never be a rational choice.

With regard to the bodybuilder analogy, I think the optimal solution will include some study of diet and nutrition and modification of your diet (it's likely to be extremely unhealthy if you're morbidly obese). Working out will be much more efficient given a strong foundation of diet and other aspects of health. Likewise with rationality, progress will be quicker if it builds upon a strong foundation of psychological health. If there isn't such a foundation already, it deserves serious attention as a high-priority sub-art.