There is no subject on which there is a greater habitual difference of judgment between a man judging for himself, and the same man judging for other people.
 John Stuart Mill, The Subjection of Women (1869). copy citation

Context

“of action of the individual—the liberty of each to govern his conduct by his own feelings of duty, and by such laws and social restraints as his own conscience can subscribe to. He who would rightly appreciate the worth of personal independence as an element of happiness, should consider the value he himself puts upon it as an ingredient of his own. There is no subject on which there is a greater habitual difference of judgment between a man judging for himself, and the same man judging for other people. When he hears others complaining that they are not allowed freedom of action—that their own will has not sufficient influence in the regulation of their affairs—his inclination is, to ask, what are their grievances?” source