In Shakespeare's "Macbeth," the line "But screw your courage to the sticking place, and we'll not fail" reflects a turning point in the narrative where Macbeth is encouraged to muster his courage for an upcoming act of treachery. This quote embodies the theme of ambition and moral conflict, as Macbeth grapples with his desire for power and the consequences of his actions. It highlights the internal struggle he faces as he decides whether to follow through with his dark intentions.

The phrase suggests that courage, when bolstered and fixed in determination, can lead to success in executing ambitious plans. However, it also foreshadows the tragic outcomes of unchecked ambition. As the story unfolds, Macbeth's initial boldness leads to a series of events that ultimately culminate in his downfall, showcasing how the pursuit of power can corrupt and destroy, particularly when combined with moral indecision.