How are the concepts of 'Kamya' and 'Nishkam' applied to spiritual practices beyond the study of texts, according to this source?

The preface in Chapter 0 introduces the concepts of 'Kamya' (with desire, for worldly prosperity) and 'Nishkam' (with a selfless mind, for liberation). However, it does so exclusively in the context of how one uses knowledge texts and Guru biographies. The text explicitly states that 'Nishkam Guru service will always be superior,' but it does not expand on how these principles of 'Kamya' and 'Nishkam' might apply to any other types of spiritual practices, meditations, or services outside the realm of studying and reciting these specific books.