I read the poem "Valediction Forbidding Mourning" in high school and
re-reading it really triggered some memories of what we talked about
in class.  One specific thing that stuck out to me re-reading was the
metaphor of the compass and their love.  I think this is a very famous
metaphor because it is so powerful.  It symbolizes that love is
symmetrical, balanced, interesting, and beautiful as it is by the
perfect circle a compass makes.  Yet at the same time it symbolizes
distance from the origin of the compass and the part of it that holds
the writing instrument.  What Donne is trying to say about the love is
that even though hey are apart they are connected in a way that cannot
separate them enough to cause harm to their love.