On the way to Capulet's party in Act I, Scene 4, Romeo tells Mercutio that he has had a dream, but before he can speak about it, Mercutio launches into his monologue about Queen Mab. Only at the end of the scene, in an aside, does Romeo reveal his thoughts. An aside is a dramatic device where a character tells his thoughts only to the audience. Other characters are still on stage, but they do not hear what is said. It is usually only a brief comment, as opposed to a monologue or soliloquy which is longer.
In these lines Romeo foreshadows the events to come, especially his own death at a very young age. He recognizes that by going to Capulet's party fate may intervene to change his life. Fate is described as: "Some consequence yet hanging in the stars." He fears this "consequence" will end in his death. Nevertheless he goes on. Fate is personified in the following lines:
But he that hath the steerage of my course
Direct my sail. On, lusty gentlemen.
Romeo, of course, is right. He meets Juliet
at the party propelling the plot toward the ultimate tragedy
of the two young lovers.