Déjà vu and love
The notion of déjà vu is used in a romanticized way to express the love. The speaker of the poem wants to express his love to the one he talks to in a way that it seems as though that love was predestined because the person was his before: "You have been mine before". It is used to express the certainty of his love and implements the notion of "souls finding each other in another life". This is that "sudden light" that the speaker of the poem experiences, and he wonders if the circle will turn around once more to make them experience the "delight" of love.
Time and death
Time moves in a circle, not linearly and the speaker of the poem wonders if the "time's eddying flight" will restore the love between the two souls that found each other again. The speaker of the poem experiences this sudden light or déjà vu that makes him "remember" his previous life and being in love with the same person he is addressing now: "You have been mine before, - How long ago I may not know". They found each other "In death's despite" and the speaker of the poem wonders if the time will let them experience the same love in this life as well.
