Letters 58.36

I shall not avoid illness by seeking death, as long as the illness is curable and does not impede my soul. I shall not lay violent hands upon myself just because I am in pain; for death under such circumstances is defeat. But if I find out that the pain must always be endured, I shall depart, not because of the pain but because it will be a hindrance to me as regards all my reasons for living. He who dies just because he is in pain is a weakling, a coward; but he who lives merely to brave out this pain, is a fool.

Seneca, Letters to Lucilius 58.36, translated by Richard Mott Gummere