A valediction forbidding mourning

The final three stanzas use an extended metaphor in which Donne compares the two individuals in the marriage to the two legs of a compass: though they each have their own purpose, they are inextricably linked at the joint or pivot at the top—that is, in their spiritual unity in God. Down on the paper—the earthly realm—one leg stays firm, just as Donne’s wife will remain steadfast in her love at home. Meanwhile the other leg describes a perfect circle around this unmoving center, so long as the center leg stays firmly grounded and does not stray. She will always lean in his direction, just like the center leg of the compass. So long as she does not stray, “Thy firmness makes my circle just, / And makes me end where I begun,” back at home (lines 35-36). They are a team, and so long as she is true to him, he will be able to return to exactly the point where they left off before his journey.