The Rambam writes that there are 13 basic truths in which every Jew should be believe. You can find them in most prayerbooks, following the daily morning service. The idea that you learned in Rosh Hashanah is not one of the basic, necessary beliefs. It may be understood allegorically, according to some authorities who maintain that non-Halachic discussions in the Gemara do not need to be understood literally. Alternatively, it may be understood to contain a message, such as the fact that life in this world is not permanent or eternal, but rather we must work hard in this world in order to earn the right to live eternally in the World to Come.

All the best,

Yisrael Shaw