It is easier to be a lover than a husband, for the same reason that it is more difficult to be witty every day, than to say bright things from time to time.

[Il est plus facile d’être amant que mari, par la raison qu’il est plus difficile d’avoir de l’esprit tous les jours que de dire de jolies choses de temps en temps.]

Honoré de Balzac (1799-1850) French novelist, playwright

Physiology of Marriage [Physiologie du Mariage], Part 1, Meditation 5 “Of the Predestined,” Aphorism 49 (1829) [tr. McSpadden]

Full text. Sometimes quoted as Aphorism 64.