Sai seems to de-emphasize the pursuit of heaven. How does this perspective relate to overcoming the fear of death and achieving true fearlessness?

In Chapter 37, the text questions the value of striving for heaven, noting that one falls from it after their merit is exhausted. It suggests that the pleasure found there is no different from sensual pleasure on earth. Instead, it elevates the importance of the earth-world, calling it the place for attaining the science of the oneness of Brahman and the Self, which is the means to ultimate liberation. This science of oneness is what truly ends the cycle of birth and death. By focusing on this ultimate good ('Shreyas') rather than the merely pleasant ('Preyas') like heaven, a person addresses the root cause of fear—the cycle of birth and death itself—thereby achieving a permanent state of fearlessness that is more profound than a temporary stay in heaven.