Art Applies: Proportions and Movement (Jaipal Cheema)

At this point, I am still reading "The Usborne Complete Book of Drawing" by Usborne. The book contains most of the basics needed to get a grasp of everyday art. In the last update, I focused on how a basic structural foundation helps further enhance any other type of drawing and skills. The book layout helps further progress me in my goal of becoming a better artist or even a decent doodler. The specific point in the book now helps bring in all the techniques learned up to this point.
The topic/technique being discussed right now is drawing animals and how exactly you draw them while they're in a particular stance or position. A big factor to this is developing a good understanding of the way proportions of guides are formatted and applied to the drawing. It states "Kittens' bodies are rounder than those of adult cats, and their heads are larger in relation to their bodies. Also, the distance between their front and back legs is shorter. Kittens are less coordinated than adults so they hold themselves differently"(Usborne 28). This quote directly shows how proportions of guidelines are changed and altered dependent on the characteristics of the figure you are attempting to draw. Not just that, they also focus on how the layout of the guides. It also states "The lowered head and drooping head whiskers give this kitten a sleepy, vulnerable look"(Usborne 28). This quote once again shows how the movement of the guide shapes affects the overall image portrayed and what the viewer pulls from the art. From this particular section, I learned a lot, but the main point I grasped was that the guides are more than just a foundation as they can be used to
show movement, as well as the size and proportion of the guides can dramatically change what the image represents. Overall, guides can be altered and built upon in ways which change the image/drawing into something that shows different characteristics.

Question: To what extent should you keep adding minute details? Is there a point at which you  actually make something worst than better by doing so? How does this apply outside of just art?
Usborne, Reece, Smith, and Brown. The Usborne Complete Book of Drawing. Usborne House, 83-85 Saffron Hill, London, EC1N 8RT, England. 1993, Print.