Why is being born on Earth considered more valuable than being in heaven for attaining fearlessness?

According to the teachings in Chapter 37, the earth-world is of profound importance, even more so than heaven. While heaven offers sensual pleasures, these are fleeting, and one falls from there after their merit is exhausted. The text points out that the earth-world is the designated place for acquiring the science of the oneness of Brahman and the Self, which is the means to ultimate liberation and fearlessness. Though life on Earth is fleeting, it is here that a person who offers every action to God can attain the place of fearlessness, making it a uniquely valuable realm for spiritual progress.