lines).  This poem, like many poems written by other metaphysical poets, centers on love, both physical and spiritual, and is presented as a dramaticmonologue.  The tone is light, informal, and highly intimate, with imagery drawn from religion (Donne was a great preacher), science, and, most interestingly, cartography.  Above all, Donne speaks to his lover about physical love and its transformation to an undying spiritual love, very reminiscent of one of his later poems to his wife, "A Valediction Forbidding Mourning."  Many metaphysical poems are framed on the if . . . then construct--that is, if this is true, then this must be the case, a very simple argument.  Although framed as a monologue, the poem assumes the assent or agreement of the listener.

Donne's light, conversational tone, fostered by Anglo-Saxon-based language, begins to develop his theme from the first line:

I wonder, by my troth, what thou and I/Did, till we loved?  Were we not wean'd till then?/But suck'd on country pleasures, childishly?

With a wonderful example of hyperbole--that they began to exist only as couple--Donne's rhetorical question establishes the quietly joyous tone and using the familiar thou rather than a more formal you.  We are silent witnesses to a private (but one-sided) conversation between two lovers whose intimacy is comfortable and deeply rooted.

The conversational tone continues in Donne's first allusion:

Or snorted we in the Seven Sleepers' den?/'Twas so, but this, all pleasures fancy be.

Donne refers to the story of seven young Christians on the run from Roman persecution who took refuge in a cave, the entrance of which was then sealed. The young people then miraculously feel asleep for almost 200 years and awoke when the cave was opened.  The allusion, however,  is less important than Donne's choice of words to describe the sleeping--"snorted we."  Normally, a poet would describe sleeping more formally, elegantly, but, in Donne's case, he is speaking to his lover with whom he has just slept.  An apt choice between intimate friends is, of course, "snorted," probably a sound they both made and heard.

In the second stanza, Donne begins the transformation of physical to spiritual love, but with a very intimate image, when he tells his lover

And now good-morrow to our waking souls,/Which watch not one another out of fear; For love all love of other sights controls,/And makes one little room of everywhere.

If we felt like we were eaves-dropping in Stanza 1, then we have left hearing behind and are watching the two lovers waking up and looking at each other. But Donne argues here that their bodies and souls are one and, more important, that fear is not part of their relationship because love, true love, has created their universe within the compass of a room.

The tone of "The Good-Morrow," then, reflects the joyous intimacy of the two lovers, so comfortable with each other that the speaker has no qualms about the somewhat inelegant "snorted we" image.  The monologue derives its immediacy from its comfortable, conversational speech, characterized by its Anglo-Saxon rather than latinate diction, and imagery grounded in the intimacy between the speaker and his silent, but undoubtedly smiling, listener. 

Let us just remind ourselves of the context of this excellent poem. The speaker is a man who is addressing a woman with whom he has spent the night. As they wake up and lie in bed together, he talks to her, describing the love that they have.

The title of the poem comes from the second stanza, as the first stanza argues that they were not really born before this point because of their lack of knowledge of love. Now however, their union has caused their souls to "wake," so the speaker bids "good morrow" to them. They have awakened to a love that is trusting and not dominated by fear. Jealousy has no part in their relationship as the purity of their love means they are not looking for other lovers:

For love all love of other sights controls,
And makes one little room an everywhere.

Their love is so complete that even the little room they are in becomes an "everywhere."

The stanza continues by considering the outer world that the lovers have given up to be together. The physical worlds that explorers seek and the spiritual world of the lovers is contrasted, and the speaker affirms that each of the lovers is a world in themselves, but at the same time arguing that they should "possess one world" through their union together. This refers to the Elizabethan belief that every human was their own miniature universe.

In his poem "The Good Morrow," Donne's main vehicle to describe his vision of love is spatial; he uses many maps, globes, and locations in the poem, and they are his way of understanding the nature of love.  In the first stanza, Donne merges time and space by wondering what he and his beloved did before they met: he imagines them inhabiting many locations separately, such as "the seven sleeper's den," and in a "country," pastoral setting.  The two lovers' meeting, however, has repositioned them to a new location.  By the third stanza, the beloved's "face" appears in the speaker's "eye," and he appears in his beloved's.  As a result, their falling in love results in a literal movement across space.  The poem also suggests that love has the power to manipulate space, in that it can "make one little room an everywhere."  Similarly, Donne employs other map and exploration metaphors when he states that he and his beloved are "two better hemispheres" than those found on the literal earth.  The poem seems to eschew actual, earthly locations (such as those that can be mapped and explored physically) for the higher level of existence embodied by love (this also resonates with his use of mythical locales like the sleeper's den and the pastoral wood).  In other words, basically, love is simply otherworldly.

STANZA ONE: The poem opens with the male speaker wondering by his “troth” (1) – that is, his good faith – what he and his beloved did before they loved. In other words, he wonders what their lives were like before they met and fell in love. He wonders, in lines 2-3, whether, in their earlier lives, they not fully mature (“not weaned” [2]) and whether they took pleasure in childish, simple things (3). Or he wonders if they snored, like the famous Biblical seven sleepers, who slept for 187 years (4). He then suddenly says that all these speculations must be true, because he now realizes that all the earlier pleasures he enjoyed, before he fell in love, were merely “fancies” – that is, insubstantial, imaginary fantasies, not real, substantive pleasure (5). He tells his beloved that if, in the past, there was any beauty that he desired and “got,” that beauty was merely a dream – a prophecy, a foreshadowing – of his beloved (6-7). These lines are especially significant, because the word “beauty” in line 6 can refer to any beautiful thing, but it can also refer to a beautiful woman. In the latter case, the word “got” can suggest sexual possession. In other words, the speaker may be admitting to his beloved that he has had sex with previous women. Such an admission implies that he trusts his beloved not to be angry or jealous. He trusts the depth of her love for him.

STANZA TWO: The speaker proclaims “good morrow” (or “good morning”) to their “waking souls” (8). This phrasing may imply that they are presently in bed together, which in turn may imply that they are married, since premarital sex was greatly criticized in Donne’s era. In any case, the speaker suggests that they have awakened spiritually (not just physically). His emphasis on their “souls” suggests that this poem celebrates true spiritual love, not mere sexual desire. In line 9 the speaker suggests that he and his beloved do not feel jealousy (a claim relevant to the use of the word “got” in line 7). In lines 10-11 he proclaims that when people are truly in love, their love affects the ways they see everything. True love can make one little room seem enormous, especially if that little room contains the beloved. In lines 12-14, the speaker invites anyone who wants to explore or map the world to do so; he says that he and his beloved, instead, can be happy in the little microcosm of their own loving relationship.

STANZA THREE: In lines 15-16, the speaker proclaims that he can see his own face reflected in his beloved’s eyes when he looks closely into them, just as she can see her own face reflected in his eyes. Their eyes reveal their true love for one another. Their love resembles a perfect sphere (a standard symbol of spiritual perfection). Anything that dies was made up of physical elements insufficiently “mixed” and thus bound to fall apart. Finally, the speaker tells his beloved that “If” (a crucial word) they can maintain their present loving, spiritual union of souls, their love will never die (20-21).

For a fine edition of Donne’s poems, see Theodore Redpath, ed., The Songs and Sonets of John Donne [sic], 2nd ed. (Cambridge, MA: Harvard University Press, 2009).

The above post gives you great historical information. You might also consider the "literary era" with which John Donne is associated.  He is usually characterized as a Metaphysical Poet and is sometimes even credited with developing this style of poetry.  The poems are marked by extremely clever and intellectual metaphors called conceits.   In this poem, he is comparing he and his love to hemispheres of earth and stating that they should be indivisible. 

He is suggesting that they are they perfect balance of the elements, and therefore are a perfect love.  He also suggests that their relationship represents the whole world.  He is certainly making a lot of grand statements!