Pain and Pleasure
Pain and pleasure are the two common descriptors for sex. In the poem, these two concepts are intertwined as a description of youthful love. Any hurt or discomfort that arises from a love affair is soothed by the sweet bliss of being loved and being with your beloved. In a sense even the pain of love itself is more desirable than the pleasure.
Fading Youth
The lovers described in the poem are young. Written from a more advanced perspective, the narrator warns them to appreciate their youthful lusts. As they age, they will grow less attractive and long for their lost youth increasingly. Youth is presented as a gift.
Time
Time is the corrupter. It steals youth, beauty, and passion from the lovers. Of all the elements of a love affair, time is the final one. It carries the lovers along on a wave of emotion, granting them blessings for stages of their lives. Time leaves behind memory as a remnant of bliss.
