What idea is conveyed through this comparison of humans to lyres

Like a lyre with strings that always make new sounds, humans respond uniquely to different experiences.

In the stanza it says that the strings of the lyres "Give various response to each varying blast". The use of the words various and varying show that the strings are always making a different sound. This idea tha things are always different is carried into the next two lines when it states that "no second motion brings/One mood or modulation like the last." This states that the sounds are not the same from one stroke to the next.  This furthers the idea that things are different. This relates back to humans in saying that humans are all different and respond differently.

the answer:

in the first part of the story running is all that matters to squeaky. running gives her confidence and defines who she is. at the beginning of the story she says that other kids call her mercury because she runs very fast. in the text she refers to herself as "miss quicksilver".

the line that provides the best evidence that squeaky has self-confidence is

" and i continue with my breathing exercise, strolling down broadway toward the ice cream man on 145th with not a care in the world cause i am miss quicksilver herself".