In a dictionary there is not much difference in their meanings but the manner in which they have been used here they come over with completely different nuances. These are perhaps the limits beyond which Epicureanism cannot be taken and where pain and pleasure become so intertwined that they lose their separateness.
Edna St. Vincent Millay
First Fig
My candle burns at both ends;
It will not last the night;
But ah, my foes, and oh, my friends--
It gives a lovely light.
I am living a more than full life that will cut short the natural span of my being but ah my enemies you have no reason to be happy in it and oh my friends do not be sorry for me. Look at the lovely light that I am shedding around me for it is a source of envy for my foes and an occasion for my well-wishers to rejoice.
- Postscript
Although I had interpreted 'But ah, my foes' in relation to envy but my subconscious self was somehow less than happy with it and in a half awake state in my bed I kept on thinking about it and the more I thought I felt that the 'source of envy' was not an appropriate and adequate expression to describe it for it negated the inherent joy, sadness, and compassion which envelope these verses - the joy at the beautiful light she radiates within her and all around her, sadness that it will not last the night, compassion for her enemies who are blind to it and she tells her friends to celebrate it rather than be sorry for her.