Like in many of Donne's poems, the narrator is attempting to convince this woman to engage in sexual relations with him by using his witty and flattering language. He praises her ability to pinpoint the exact moment of most pleasure in his dream and wake him from it right then. THe narrator does not mind, because he would rather be awake in her presence and continue the act that he began in the dream, but in reality. He even claims the act in his dream was much too strong for fantasy. He believes the woman is interested in engaging in this act with him, but in the last stanza of the poem she seems to rethink the idea and the narrator is not happy with it.
Coming and staying show'd thee, thee,
But rising makes me doubt, that now
Thou art not thou.
Because she came in and woke him at just the right time, he is happy, but because she gets up to leave (likely from doubt about engaging in any pre-marital sexual acts) he doubts her.
That love is weak where fear's as strong as he ;
'Tis not all spirit, pure and brave,
If mixture it of fear, shame, honour have ;
He attempts to convince her that it is ok by telling her to have honor, and not allow fear and shame to overpower love.
Perchance as torches, which must ready be,
Men light and put out, so thou deal'st with me ;
Thou camest to kindle, go'st to come ; then I
Will dream that hope again, but else would die.
Finally he starts to conjecture about what she is doing, comparing her doubt to engage in any act with him to men lighting and putting out torches. He closes but stating that since he cannot have her in reality, he must dream about the act again and withou it he would die.