One quote which causes Montag to assess his life and the society in which he lives is Clarisse's question, "Are you happy?"
In Chapter 1 of Fahrenheit 451, Montag walks home one night and, while doing so, he again feels as though someone is there because the "air seemed charged with a special calm" from a person who has waited there, then moved to let him through. But, this night, she appears and tells him her name is Clarisse McClellan and walks along with him. As they talk, Clarisse notes that Montag laughs when she has not said anything funny, and he answers so quickly that it is clear that he has not thought about what she asks. Then, Clarisse mentions a number of sights to which Montag has paid no attention.
Finally, before parting with him, she asks Montag, "Are you happy?" and quickly runs off. As he continues toward his house, Montag thinks, "Happy? Of all the nonsense." But, when he opens his front door and enters the silent rooms, he finds this odd girl's face on the blank wall, as though it were a mirror. "What incredible power of identification the girl had," he reflects.
After this reflection, Montag opens the bedroom door, and the room now seems like "a mausoleum after the moon has set." Then, in the darkness, Montag realizes
He was not happy. He wore his happiness like a mask and the girl had run off across the lawn with the mask and...there was no way of going...and getting it back.
From this pivotal night on, Montag changes his perspective, examining his life with a clearer vision. He becomes aware of his lifeless and loveless marriage with Mildred, as well as the impersonal and tragic nature of his society that immerses itself in empty hours with modern technologies that do nothing for the human soul as only books can.