Letters 70.14

You can find men who have gone so far as to profess wisdom and yet maintain that one should not offer violence to one’s own life, and hold it accursed for a man to be the means of his own destruction; we should wait, say they, for the end decreed by nature. But one who says this does not see that he is shutting off the path to freedom. The best thing which eternal law ever ordained was that it allowed to us one entrance into life, but many exits.

Seneca, Letters to Lucilius 70.14, translated by Richard Mott Gummere