Juliet was anxious to speak out her feelings and the thoughts on her mind, bat the same time she doesn't want to appear to be too hurried. she also had a bitter feeling about the conversation that they have had tonight. she claims to be of no joy regarding the conversation because it is "too rash". Also, she had told her mother that he had no idea of love or marriage until that time.
Juliet was concerned that they are falling in love too fast (it can come
and go like lightning)