Can you please help me explain the theme of this poem?

In this poem inson is viewing life through the perspective of death which is like a carriage that stopped to pick her up. She sees herself as immortal, simply a reflection of her life that ends in the grave (A swelling in the ground, roof scarcely visible, cornice a mound). Death is a kindness that civilly allows her to out away the burdens of life. Time disappears, centuries become shorter than a day from the moment she first realises that death's journey is towards eternity.