If I can stop one heart from breaking,

I shall not live in vain;

If I can ease one life the aching,

Or cool one pain,

Or help one fainting robin

Unto his nest again,

I shall not live in vain.

—“If I Can Stop One Heart from Breaking,"
Emily Dickinson

Based on the repetition of “I shall not live in vain,” what is most likely the subject of the poem?

living life without pain
living life with questions
living life with a purpose
living life without worry