In Scene 1, Juliet expresses fears that Romeo will be discovered and killed, and that their love will not last. In the final scene, Juliet fears Romeo's love has faded and she will be left alone in the tomb.
In Scene 1 of Romeo and Juliet, Juliet expresses two fears. First, she fears that Romeo will be discovered and killed due to the hatred between their families. She says, "Prodigious birth of love it is to me / That I must love a loathed enemy" (Act 1, Scene 5). Second, she fears that their love will not last and will be too good to be true. She says, "It is too rash, too unadvised, too sudden; / Too like the lightning, which doth cease to be / Ere one can say 'It lightens'" (Act 1, Scene 5).
Later in the play, towards the end, Juliet faces these fears. In the tomb, she fears that Romeo's love for her has faded and he will not stay true to her forever. She says, "...that unsubstantial Death is amorous, / And that the lean abhorred monster keeps / Thee here in dark to be his paramour?" (Act 5, Scene 3).
Additionally, she fears being left alone in the tomb and the darkness and silence that surrounds her. She says, "...What if this mixture do not work at all? / Shall I be married then tomorrow morning? / No, no! This shall forbid it. Lie thou there" (Act 5, Scene 3).