When talking to Balthasar, Romeo is forceful and confident. He tells Balthasar his errand is simply to see Juliet and take a ring from her finger. He orders Balthasar not to follow and insists he will see Balthasar soon.
However, when alone with Juliet, Romeo is downcast. He is mourning the loss of life in the case of Tybalt, Paris and Juliet. He sees little purpose in it all and is unable to go on with his grief. When with Juliet, he is himself and more as he was in Act I, when grieving over Rosaline's rejection.