The poem is an elegy and uses paradox and antithesis to present the tragedy of poet’s situation clearly. Antithesis means setting opposites against each other: prime of youth / frost of cares (from the first line). While paradox is self-contradictory statements, yet true which can be found in every line of every stanza in this poem.
The poet’s metaphorical skill is coupled with a clever use of tense to suggest the blurring of past and present. The repetition of “now” in the last line of each stanza has the effect of suggesting a passage of time so swift that past and present are telescoped: “And now I live, and now my life is done.”
The poem is expressing the feeling of a young person awaiting his death and what goes on the person’s mind. Along the message that no one wants to die young. The executing order soon to be implemented makes him recall his short life and makes him evaluate what life has given to him. Like the execution, the poet considers that everything in life is unexpected and unnatural.