The speaker plays on two meanings of "will." The first is the legal document that says who gets what after you die. The second is willingness, the desire to keep living and to act. By saying he "broke up" with his will, as if ending a relationship, he makes a grim bit of paperwork sound almost casual, even wry. Yet he admits he feels "left empty," so the break has cost him something.
The poem then turns, quietly. He could be "willing again / in an hour," which suggests his mood shifts easily and that despair isn't final. What he hopes for is modest: to "make some use of age" without help, keeping his independence. The last lines widen out to a "globe so troubled / and strange to me now," so the world itself feels unfamiliar. The mood is tired and uncertain, but it is also stubborn, with a small, dry hope running underneath.