Hardly a line passes by in Beowulf without the narrator reminding us that everyone is going to die eventually. It's really a very morbid poem, in fact. The awareness of death is a constant for medieval Scandinavian warriors, who kill their enemies and watch their friends die on a daily basis. In a life filled with uncertainty and violence, these fighters must accept that everyone shares the same fate – death. What matters, then, is to keep one's eventual death constantly in mind and try to perform great deeds so that you can be remembered by those who live after you as a great warrior.
By remaining constantly aware of their own mortality, warriors in Beowulf prevent themselves from becoming overconfident in their own prowess and abilities.
Medieval Scandinavian warriors seek an immorality on earth by establishing their reputations as heroes.