What gives Juliet the strength to drink the potion?

At the end of Act IV, Scene III, Juliet is alone in her bedroom trying to work up the courage to drink the sleeping potion prepared for her by the Apothecary. If all goes according to plan, Juliet will sleep so deeply that she appears dead and will awake when Romeo comes to find her in her family tomb. Juliet's courage begins to shake as she wonders whether the potion will work at all, or...

At the end of Act IV, Scene III, Juliet is alone in her bedroom trying to work up the courage to drink the sleeping potion prepared for her by the Apothecary. If all goes according to plan, Juliet will sleep so deeply that she appears dead and will awake when Romeo comes to find her in her family tomb. Juliet's courage begins to shake as she wonders whether the potion will work at all, or whether it might really kill her! She works herself up into a frenzy, dreading what might happen if she wakes up too early in the tomb, alone with her dead ancestors. She even thinks that she sees Tybalt's ghost, come back to hunt down Romeo. With this, she steels herself and defiantly drinks the potion, setting her mind on the hope that she will awake in the tomb, according to plan.