Read these stanzas from the poem "Ballad" by Paul Laurence Dunbar. I know my love is true, And oh the day is fair. The sky is dear and blue, The flowers are rich of hue, The air I breathe is rare, I have no grief or care; For my own love is true, And oh the day is fair. My love is false I find, And oh the day is dark. Blows sadly down the wind, While sorrow holds my mind; I do not hear the lark, For quenched is life's dear spark,— My love is false I find, And oh the day is dark! What is the central idea of this poem?