When Romeo woke up that morning in act 5 scene 1 of Shakespeare's Romeo and Juliet, he was feeling pretty good. The night before, he had a dream about Juliet.
ROMEO. I dreamt my lady came and found me dead
(Strange dream that gives a dead man leave to think!)
And breath'd such life with kisses in my lips
That I reviv'd and was an emperor. (5.1.6-9)
Romeo remarks that being in love is wonderful, and even his dreams are happy.
ROMEO. Ah me! how sweet is love itself possess'd,
When but love's shadows are so rich in joy! (5.1.10-11)
Romeo's serving man, Balthasar, arrives, and Romeo peppers him with questions for news from Verona.
ROMEO. News from Verona! How now, Balthasar?
Dost thou not bring me letters from the friar?
How doth my lady? Is my father well?
How fares my Juliet? That I ask again,
For nothing can be ill if she be well. (5.1.12-16).
Balthasar tries to delay telling Romeo that Juliet is dead (or appears to be dead), and that she's been laid to rest in the Capulets' tomb.
BALTHASAR. Then she is well, and nothing can be ill. (5.1.17)
Shakespeare did a similar play on words in Macbeth when Ross comes to tell Macduff that his wife and children had been killed on Macbeth's order.
MACDUFF. How does my wife?
ROSS. Why, well.
MACDUFF. And all my children?
ROSS. Well too.
MACDUFF. The tyrant has not batter'd at their peace?
ROSS. No; they were well at peace when I did leave 'em. (Macbeth, 4.3.199-204)
This is a way for Shakespeare to create suspense as to what reaction either Romeo or Macduff will have when they hear the truth.
Macduff is stunned and disbelieving. He repeatedly asks Ross to confirm that his wife and children are dead.
In contrast, Romeo is instantly enraged, and he goes directly into action. He curses his fate, calls for ink and paper (although no further mention of writing a letter appears in the play), and he orders Balthasar to hire horses so he can return to Verona as soon as possible.
ROMEO. Is it e'en so? Then I defy you, stars!
Thou knowest my lodging. Get me ink and paper
And hire posthorses. I will hence to-night. (5.1.24-26)
"Then I defy you, Stars!" can be interpreted as Romeo cursing his fate, or as Romeo intending to take fate into his own hands to resolve the matter of Juliet's death.
It's hard to know if, at that moment, Romeo has already decided to kill himself, although there are just a few more lines of conversation with Balthasar before Romeo makes his intentions clear.
ROMEO. Well, Juliet, I will lie with thee to-night.
Let's see for means. O mischief, thou art swift
To enter in the thoughts of desperate men!
I do remember an apothecary... (5.1.36-39)
It's interesting that Romeo never asks Balthasar how Juliet died, or asks him anything about the circumstances of her death.
At first it seems as though Romeo wants to hurry back to Verona to find out what happened to Juliet, or perhaps to avenge her death. It appears, however, that Romeo doesn't really care how Juliet died, only that she's dead. Immediately upon hearing the news, he's decided to die by her side.