The ability to discern or discriminate between the real and unreal, eternal and temporary is one of the key elements in a spiritual practice and essential for achieving moksha, or spiritual liberation. A great Hindu philosopher, Adi Shankara, wrote a famous poem titled, "Vivekachudamani," where he described viveka and its importance on the path to liberation.
Viveka is an important aspect in the physical practice of yoga as well. It shows one's skill in discerning the details in one's alignment, by turning one's attention inward and working with the invisible details. Learning to detect the details about one's yoga practice helps to improve the practice itself, but can also increase the quality of "off the mat" experiences as well.