Why is the earth-world considered more important than heaven for achieving a state of fearlessness?

Chapter 37 presents a compelling argument for the superiority of the earth-world over heavenly realms for spiritual attainment. It dismisses the allure of heaven by noting that sensual pleasures are ultimately the same everywhere and that heavenly status is temporary, ending once one's merit is exhausted. The earth-world, in contrast, is described as the unique and profound place for practicing the 'science of the oneness of Brahman and the Self.' Although life on earth is fleeting, it offers the opportunity to offer every action to God. As the text states, one who does this 'attains the place of fearlessness,' which is ultimate liberation and far more valuable than the transient rewards of heaven.