Juliet uses both logic and emotion to make her decision, but her emotions ultimately help her decide. She struggles with many internal fears as she builds up her nerve to take the potion that Friar Laurence has given her. She feels that her family has betrayed her by forcing her to marry Count Paris. She feels bad about lying to her family and going against them and wishes that things could go back to the way they were.
After she realizes she must be mature and make this decision by herself, Juliet has to overcome her fears about the potion. She briefly doubts Friar Laurence, but immediately reminds herself that he is a holy man and that she can trust him:
I fear it is: and yet, methinks, it should not,
For he hath still been tried a holy man.
Since the potion is alien to her, Juliet doesn’t know if it’ll work properly. She’s worried about what will happen if she wakes up before Romeo arrives to save her and she suffocates and dies in the tomb:
Shall I not, then, be stifled in the vault,
To whose foul mouth no healthsome air breathes in,
And there die strangled ere my Romeo comes?
Despite all her fears, when Juliet imagines that Tybalt’s ghost will try to kill Romeo for revenge, she makes up her mind to drink the potion and hope that everything works out with Romeo. In the end, it’s clear that Juliet’s love for Romeo helps her to overcome her fears and to make her decision to drink the potion.