Why was the defeat over Grendel so important to King Hrothgar?

King Hrothgar was in disgrace. Grendel, a demon and descendant of Cain had been assaulting Heorot for years, taking the people that he as king was sworn to protect essentially right from under his guard and care.

The situation had become so dire that the Danes had even forsaken God and had taken up idols and called on the devil hoping for some relief from their problem.

Basically, for Hrothgar, defeat of Grendel was everything to him. He had lost his honor, his kingdom, and his faith...and he and his people were all completely at the mercy of Grendel and, unless Grendel could be defeated, all of these were completely lost to him.

So basically, if everything that defined both your physical and spiritual self were wrapped up in the defeat of a being, it would probably be rather important for you as well.