What is the true purpose of human life (Purushartha) as outlined in Chapter 17, and how is it achieved?

As detailed in Chapter 17, the true purpose of human life, or Purushartha, is to discard the pleasant path of worldly joy (Preya) and consciously honor the good path of salvation (Shreya). This is likened to a swan that drinks only the pure milk when it is mixed with water. Achieving this, the chapter explains, requires true human effort and strengthening one's intellect to struggle for the sake of Shreya. One must first definitively understand where Shreya lies and then develop the firmness, like Dattatreya, to resist the obstacles that arise on this spiritual path.