From the winter of 1821, when I first read Bentham, and especially from the commencement of the Westminster Review, I had what might truly be called an object in life; to be a reformer of the world. My conception of my own happiness was entirely identified with this object. The personal sympathies I wished for were those of fellow labourers in this enterprise. I endeavoured to pick up as many flowers as I could by the way; but as a serious and permanent personal satisfaction to rest upon, my whole reliance was placed on this; and I was accustomed to felicitate myself on the certainty of a happy life which I enjoyed, through placing my happiness in something durable and distant, in which some progress might be always making, while it could never be exhausted by complete attainment. This did very well for several years, during which the general improvement going on in the world and the idea of myself as engaged with others in struggling to promote it, seemed enough to fill up an interesting and animated existence. But the time came when I awakened from this as from a dream. It was in the autumn of 1826. I was in a dull state of nerves, such as everybody is occasionally liable to; unsusceptible to enjoyment or pleasurable excitement; one of those moods when what is pleasure at other times, becomes insipid or indifferent; the state, I should think, in which converts to Methodism usually are, when smitten by their first “conviction of sin.” In this frame of mind it occurred to me to put the question directly to myself: “Suppose that all your objects in life were realized; that all the changes in institutions and opinions which you are looking forward to, could be completely effected at this very instant: would this be a great joy and happiness to you?” And an irrepressible self-consciousness distinctly answered, “No!” At this my heart sank within me: the whole foundation on which my life was constructed fell down. All my happiness was to have been found in the continual pursuit of this end. The end had ceased to charm, and how could there ever again be any interest in the means? I seemed to have nothing left to live for.

Note from KBJ: This is the most poignant paragraph in the book, in my opinion. Try to imagine how Mill felt, having spent every minute of every waking hour of his 20-year life learning (and applying) the utilitarian system. All of a sudden, it meant nothing to him. His life seemed pointless, empty, aimless, meaningless. Others have probably had this experience when they stopped believing in God. Utilitarianism was Mill's god. It's fortunate for all of us that Mill didn't kill himself during this awful period of his life, for he went on to produce many great works of philosophy. As you will see, it took him years to put solid ground back under his feet.