A quote
All things that Fortune looks upon become productive and pleasant, only if he who possesses them is in possession also of himself, and is not in the power of that which belongs to him. For men make a mistake, my dear Lucilius, if they hold that anything good, or evil either, is bestowed upon us by Fortune; it is simply the raw material of Goods and Ills that she gives to us—the sources of things which, in our keeping, will develop into good or ill. For the soul is more powerful than any sort of Fortune; by its own agency it guides its affairs in either direction, and of its own power it can produce a happy life, or a wretched one.
Seneca·Letter 98 — On the Fickleness of Fortune (§2)·trans. Gummere