Chapter 17 uses an analogy of a swan and milk. Can you explain this analogy and how it relates to the choice between Shreya and Preya?

In Chapter 17, the text explains that Shreya (the path of salvation) and Preya (the path of worldly joy) are often blended together, just like milk and water. The analogy of the swan, or Maral, is used to illustrate how a wise person navigates this mixture. Just as a swan is said to be able to drink only the pure milk from a mix, leaving the water behind, a courageous and intelligent person clings only to Shreya. As Chapter 17 clarifies, these fortunate souls always turn away from Preya, while dull-witted individuals, caught in worldly concerns, pursue the pleasant but ultimately unfulfilling path of Preya.