Letters 70.12

Moreover, just as a long-drawn out life does not necessarily mean a better one, so a long-drawn-out death necessarily means a worse one. There is no occasion when the soul should be humoured more than at the moment of death. Let the soul depart as it feels itself impelled to go; whether it seeks the sword, or the halter, or some draught that attacks the veins, let it proceed and burst the bonds of its slavery. Every man ought to make his life acceptable to others besides himself, but his death to himself alone. The best form of death is the one we like.

Seneca, Letters to Lucilius 70.12, translated by Richard Mott Gummere