Letters 24.24

Whichever of these ideas you ponder, you will strengthen your mind for the endurance alike of death and of life. For we need to be warned and strengthened in both directions,—not to love or to hate life overmuch; even when reason advises us to make an end of it, the impulse is not to be adopted without reflection or at headlong speed.

Seneca, Letters to Lucilius 24.24, translated by Richard Mott Gummere