What you hear affects your emotions. Whether it is what someone is saying to you, a song that is happy or sad, an annoying dog, hearing others arguing or the sound of tree leaves rustling in a gentle breeze. Life would be extremely different without being able to hear.
Muscles provide a beautiful allegory for life and character. There is something spiritual that develops in a person's character when choosing to learn and grow, harvesting beauty from ashes rather than seething in bitterness.