The writer of a reflective essay examines (or reflects) on their life, and then writes about it. If one were to write a reflective essay about a poem, one would write about the feelings the poem elicits.
In this case, you might write about your feelings toward the author's attitude. Are you part of a lost generation? What emotions do you feel when someone suggests hopelessness in the world?
You might also discuss how you felt when you read the poem backwards and realized that the authors purpose was not to offer a dire outlook, but to suggest that things can change if viewed in the proper perspective (or you could write about how much it angered you that whoever presented this poem to you gave it to you upside down because you're definitely supposed to read it beginning with "I am part of a lost generation," and then realize that you can read it the other, more hopeful way).
How did it make you feel to discover that you could read the poem sensibly in either direction? Are there times in your life that you view negatively that could benefit from such a shift in perspective? Are there times in your life in which you had disagreements with others--maybe disagreements that ended relationships, whether platonic or romantic--that, upon reflection, were due to differing perspectives? Would realizing that two people will extract different information from the exact situation have helped you in that situation?
You could choose a couple of lines, even out of context, and focus on those and whatever you felt when you came upon those words (if you're pursuing an English degree, they'll make you do this in classes at the 300 level and higher). Are you a child of divorced parents? What are your thoughts on divorce rates and their impact to children?
Do you have strong feelings regarding environmentalism?
I think you can take it from here.
