How does Chapter 17 illustrate the difficulty of choosing Shreya over Preya, and who succeeds in this choice?

In Chapter 17, the challenge of choosing the good (Shreya) over the pleasant (Preya) is compared to separating milk from water when they are mixed. The text explains that while the choice is within a person's control, it is difficult for a dull-witted person who is conquered by Preya. These individuals, caught in the cycle of maintaining their body, wealth, and status, find Preya to be sweet. However, the chapter also notes that courageous, intelligent, and wise individuals, likened to a swan that drinks only the pure milk, are able to cling to Shreya and turn away from worldly temptations.