Oh, the poem dates from between 1330 and 1340 -- call it 1335. Its roots are found in the Greek story of Orpheus, who attempted to rescue his wife from Hades, only to look back and lose her forever.

That story is, of course, symbolic of an addiction (wife = addiction + his desire to be "clean", a classic dichotomy) to sweets (wife also = "sweet thing") and Orpheus's vain attempt to overcome it. His descent into Hades (the hell of his addiction), his permission to free his "wife" on the condition that he never look back (at his addiction), his failure to fulfill the condition (i.e., backsliding), and his failure to overcome his addiction and to kick his habit.

This is, of course, a very, very quick summary of the reality underlying both the ur-poem and the poem quoted. To fully understand the ur-poem, you must read it in the original Attic Greek, of course.