What does Beowulf learn from his battles with Grendel and Grendel's mother?

When Beowulf is in the battle with Grendel and his mom, he learns how to be tactful and resourceful. He learns that battles don't always go as planned and that sometimes improvising might be necessary. An example of this is when the sword he took underwater wouldn't kill Grendel's mother, so he had to use the resources he had under water. In the end he ended up using the only sword that would kill Grendel's mother, that he found while he was in battle with her.

I also think he learned that to be a great king he needs to make sacrifices that have the best interest of his people. Whether it was a military or personal sacrifice. In this case it was to sacrifice himself and some of the geats to serve in another city to hopefully help out his fellow men, even though it didn't directly effect him.