This poem, written in 1633, is about sensual love that is so powerful it is spiritual.
In "The Good-Morrow," the speaker awakens next to his lover and considers their love. In a hyperbolic statement, the speaker asks the woman what they did prior to meeting and falling in love and/or spending the night together. He suggests that they childishly engaged in earthly pleasures. This could mean that prior to their meeting/love making, they were mere children; their lives had barely begun. More likely, it means that they engaged in sexual pleasures but these were childish and therefore nothing compared to what they had then and there. He concludes the first stanza saying that anything beautiful he'd experienced prior to meeting his lover was a dream of hopefully meeting her someday, which in this day and age, sounds like a bad pick up line.
The reference "Seven Sleepers" in that first stanza refers to a legend of persecuted Christians sleeping in a den for hundreds of years. They had to hide for fear of expressing their beliefs. In "The Good-Morrow," the speaker suggests that, prior to this open expression of love, his and his lover's lives had been as if they were hiding because this new world of their love is so liberating.
In the second stanza, the speaker does not have to worry about jealousy; they do not have to watch one another. Their love is so deep that each one of them is a world and therefor, the world of their love, the "little room" they are in "is an everywhere."
In the third stanza, he looks at himself reflected in her eyes and she sees her reflection in his. The two hemispheres could be their faces or their bodies, each a half of one whole world. Their love can not be contained by direction or dimension (north and west). It is beyond the physical now. In the final lines, their love is elevated to the spiritual.
Whatever dies was not mixed equally;
If our two loves be one, or, thou and I
Love so alike, that none do slacken, none can die.
Mortal and earthly substances die because they are "not mixed equally," meaning that their mixture is not complete, whole, or absolutely united and therefor done changing (timeless). Their love is timeless because it is whole, completely united (mixed). That is like saying two hemispheres making one whole world. A love such as this is perfect in its total completion. Being perfect, it is immortal and can not die.