At the beginning of the song the speaker says that he "walked across an empty land." This "empty land" is a metaphor, and it represents the emptiness and disorientation that the speaker feels now that he has lost the person he loves. He goes on to say that he used to know the pathway on this land "like the back of his hand." This simile suggests that he used to know very well his way across this land, perhaps because he used to walk across it with the person he loved. The overall implication is that the speaker now feels lonely in familiar places because he is without the person he loves and who used to accompany him in these places.
Later in the song the speaker says that he "came across a fallen tree." This tree is an example of symbolism. It symbolizes the loss of the love between the speaker and the person he has lost, or, more broadly, it symbolizes their relationship, which, like the tree, has fallen. This idea is emphasized when the speaker asks of the place with the fallen tree, "Is this the place we used to love?"
In the second half of the song the speaker repeats the line that reads "this could be the end of everything." This is an example of hyperbole or exaggeration. The implication of the line is that, without the person he loves, the speaker feels as if the whole world might end. The repetition of this line emphasizes just how sad and how lost the speaker feels without the person he loves and how desperate he is for that person to come back to him.