In the first of these soliloquies, Juliet is awaiting the arrival of Romeo, her new husband, at her bedchamber. She is longing for the daytime to be over so that he can come under the cover of night, without being seen or discovered. She speaks to the "gentle night," addressing it directly, asking that—after her own death—Romeo be "cut [...] out" into the shapes of stars so that he can decorate the "face of heaven" and make everyone love night and "pay no worship to the garish sun."
This speech contains a great deal of foreshadowing as a result of Juliet's love of nighttime and her desire to see Romeo placed with the stars. Earlier in the play, during the balcony scene, Romeo had belittled the "envious moon" and compared Juliet to the "fair sun." If she is like the sun, and he is like the stars, then the two of them can never be together because the sun and stars do not appear in the sky together (to our eyes, at least). Their contrasting comparisons seem to bode ill for their future together and add to the idea that they simply cannot be.
In the second of these soliloquies, we see Juliet just as she is about to drink the draught that will make her appear to be dead. She fears that she will wake up in the tomb, that Romeo will not be there, and that she will die before anyone finds her. She considers death and how she is willing to risk it for the chance to live her life with Romeo. We see, here, what an active agent Juliet truly is and how brave she is. It is, most often, Juliet that moves the plot forward: she asks Romeo about marriage, offering to send a messenger to him. She refuses to marry Paris. She goes to the friar in order to enlist his help in avoiding the marriage, and she's even willing to kill herself to avoid it. She decides to fake her own death in order to be with Romeo. This soliloquy shows her continued commitment to him and their relationship. Shakespeare seems to make her the stronger and more thoughtful character when compared to Romeo.