Seneca · On the true joy which comes from philosophy
Letters 23.3
Above all, my dear Lucilius, make this your business: learn how to feel joy.
Do you think that I am now robbing you of many pleasures when I try to do away with the gifts of chance, when I counsel the avoidance of hope, the sweetest thing that gladdens our hearts? Quite the contrary; I do not wish you ever to be deprived of gladness. I would have it born in your house; and it is born there, if only it be inside of you. Other objects of cheer do not fill a man’s bosom; they merely smooth his brow and are inconstant,—unless perhaps you believe that he who laughs has joy. The very soul must be happy and confident, lifted above every circumstance.
Seneca, Letters to Lucilius 23.3, translated by Richard Mott Gummere