Wyrd In Beowulf
How do the concepts of 'wyrd' and 'fate' influence or affect Beowulf's actions throughout the poem?
My only issue with your question is that the Anglo Saxon concept of "wyrd" and our word "fate" mean precisely the same thing. (The more "Christian" word for it all would be "providence.") Once you begin thinking of it as wyrd/fate, it's much easier to understand.
There are many quotes that can exemplify this idea. For example, even though Grendel was notorious, he could have killed more men, but it was wyrd/fate that kept him from doing so. The narrator says that Grendel would have slain more
except God in his wisdom and the man's courageous spirit had withstood that wyrd and him. The Lord ruled all the human race as he still does.
There is also no way of getting around the Christian influence of wyrd/fate here in the hand of "providence." Note the words "God" and "wisdom" and "the Lord" and "ruled." One god. Monotheism. Christianity. Not the original paganism of the Anglo Saxons. Here it is precisely God that moves the actions and the doings of all men. There is a plan in place for what happens on the earth. And yet, all things that happen are due to free will. In this regard wyrd/fate is more than just some kind of "blind force" that determines everything. Free will prevents that.
Another perfect example of wyrd/fate can be found later in the book and is said by Beowulf himself:
Each of us must await the end of his path in this world, and he who can, should achieve renown before death! That is the best memorial when life is past and a warrior's days are recounted!
Here Beowulf reflects on the "path" that everyone must take in the world. Note the idea of free will in the phrase "who can." Beowulf is saying that if you can achieve fame or "renown" before death by doing something good for the country and its people, that is the best epitaph anyone can have. This not only reflects Beowulf's belief in wyrd/fate, but also his impression of immortality.
"Wyrd" is a concept that pervades Anglo-Saxon poetry in all genres. In "The Wanderer" for example, we see the phrase "wyrd bith ful araed," which translates roughly to "Fate is fully exorable"—humans can do nothing to alter what fate has decreed. In Beowulf, we see the same idea: "Gæð a wyrd swa hio scel!" (Fate goes ever as it/she will.) The characters in Beowulf believe that there is ultimately nothing they can do to change the course fate has laid out for them. It is notable that "fate" seems to define the most important moments of one's life, such as the time of one's death, but people can still change the smaller things that happen around these dictates of "wyrd"—hence why Beowulf is so concerned with doing as many glorious deeds as he can in life, so that he will be remembered by reputation after Wyrd has led him to his death. Compare the medieval Boethian concepts of providence and fate.
In Beowulf, there are numerous instances where a belief in the dictates of wyrd affect behavior. In the digressions, we see that the Beowulf poet himself believes that fate is responsible for the deaths of many great warriors, regardless of their actions; this same idea is strong in Beowulf himself, and in keeping with the theme of "ofermod" or pride which pervades the story, it drives him to secure his fame in life. At the end of the poem, it is stated that Beowulf was sad of heart because of an awareness that his "wyrd" drew near. This moves him to tell the story of his earlier battles to those still able to listen. (line 2419) When his tale is concluded, he states that he will not flee from death, for "it must happen at the wall, as Fate allots us" (2526).
There are several examples of this. One example is when Beowulf decides he will fight Grendel barehanded. My translation (Burton Raffel) reads "Fate will unwind as it must." Later when Beowulf fights the dragon, my translation reads: "... And for the first time in his life that famous prince fought with fate against him, with glory denied him. He knew it, but he raised his sword and struck at the dragon's scaly hide..."