In Act IV, scene 1, Juliet has recently been told by her father that she is to marry Paris. Of course, she cannot do this because she has already married Romeo. Rushing to the cell of Friar Laurence, she encounters--of all people--Paris, whom she greets coolly, but cordially. After Paris tells her that he will meet her on Thursday and "early will I rouse ye," and he leaves, Juliet despairingly drops to her knees, entreating the Friar,
Oh, shut the door, and when thou hast done so,
Come weep with me--past hope, past cure, past help! (4.4.45)
These short phrases in repetition and in parallel structure indicate Juliet's utter despair that cannot be assuaged with words. Her bleak expression of her life is only summarily and abruptly expressed as she feels her happiness completely destroyed. To Juliet, there is no future.
After Paris, who thinks that Juliet will marry him, tells her that he will see her on Thursday for their wedding, Juliet says to Friar Lawrence: "O, shut the door! And when thou hast done so, Come weep with me, past hope, past cure, past help." These lines help us understand that Juliet looks to the friar for companionship, as she wants to weep with him. Her use of parallelism emphasizes her despair at having to marry Paris when she is already wed to Romeo. She feels that there is no reason for hope, no solution to her problem, and no one to help her. The parallel structure lets the reader know how distraught and hopeless Juliet feels and explains why she later embraces the Friar's plan for her to take a potion that will make her appear dead. She would not embrace this measure unless she were desperate, and she allows the Friar to convince her of its utility because he (and the nurse) are the only help she has.