How does Chapter 17 use the analogy of a swan to illustrate the choice between spiritual good and worldly pleasure?

In Chapter 17, a powerful analogy is used to describe the discerning choice between Shreya (the good) and Preya (the pleasant). The text states that just as water and milk can be mixed, so too are these two paths blended in life. However, a swan, referred to as a 'Maral,' is said to possess the unique ability to drink only the pure milk from the mixture, leaving the water behind. According to Chapter 17, courageous, intelligent, and wise people are like this swan; they are able to discriminate and cling only to Shreya, the path of salvation, while consciously turning away from the alluring but ultimately unfulfilling path of Preya.