Letters 94.74

Then they fear that for which they strove, and the good fortune which made them weighty in the eyes of others weighs more heavily upon themselves. Then they praise easy leisure and independence; they hate the glamour and try to escape while their fortunes are still unimpaired. Then at last you may see them studying philosophy amid their fear, and hunting sound advice when their fortunes go awry. For these two things are, as it were, at opposite poles—good fortune and good sense; that is why we are wiser when in the midst of adversity. It is prosperity that takes away righteousness. Farewell.

Seneca, Letters to Lucilius 94.74, translated by Richard Mott Gummere