How does Chapter 17 use the analogy of a swan to explain the choice between Shreya and Preya?

In Chapter 17, the text presents a powerful analogy to illustrate how a discerning individual chooses the spiritual path. It states that just as water and milk can be mixed, so are Shreya (the good) and Preya (the pleasant) blended in life. However, a mythical swan, or Maral, is said to be able to drink only the pure milk from such a mixture. Similarly, as Chapter 17 explains, courageous, intelligent, and wise individuals are like these swans; they cling only to Shreya and turn away from Preya. In contrast, the dull-witted get caught in worldly pursuits and embrace Preya, unable to make this crucial distinction.