Epictetus

“ What is the position of the layman, and what that of the philosopher?
The first difference between a layman and a philosopher: The one says, "Woe is me because of my child, my brother, woe because of my father"; and the other, if he can ever be compelled to say, "Woe is me," adds, after a pause, "because of myself." For nothing outside the sphere of the moral purpose can hamper or injure the moral purpose; it alone can hamper or injure itself. ”

“ If, then, we too tend in this latter direction so that, whenever we go amiss, we blame ourselves, and bear in mind that nothing but judgement is responsible for the disturbance of our peace of mind and our inconstancy, I swear to you by all the gods that we have been making progress. ”