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No man can live happily who regards himself alone, who turns everything to his own advantage. Thou must live for another, if thou wishest to live for thyself.

"Hoyt's New Cyclopedia Of Practical Quotations" by Jehiel Keeler Hoyt, p. 350-52, Epistolæ Ad Lucilium, XLVIII, 1922.
No man can live happily who regards himself alone, who turns everything to his own advantage. Thou must live for another, if thou wishest to live for thyself.