Hope itself is a species of happiness, and perhaps, the chief happiness which this world affords: but, like all other pleasures immoderately enjoyed, the excesses of hope must be expiated by pain; and expectations improperly indulged, must end in disappointment. If it be asked, what is the improper expectation which it is dangerous to indulge, experience will quickly answer, that it is such expectation as is dictated not by reason, but by desire; expectation raised, not by the common occurrences of life, but by the wants of the expectant; an expectation that requires the common course of things to be changed, and the general rules of action to be broken.
–Samuel Johnson, in Boswell’s Life