Seneca - The blows of Fortune

No man has been shattered by the blows of Fortune unless he was first deceived by her favours. Those who loved her gifts as if they were their own for ever, who wanted to be admired on account of them, are laid low and grieve when the false and transient pleasures desert their vain and childish minds, ignorant of every stable pleasure. But the man who is not puffed up in good times does not collapse either when they change. His fortitude is already tested and he maintains a mind unconquered in the face of either condition: for in the midst of prosperity he has tried his own strength against adversity.

Seneca, source Brainpickings