Why did Epictetus teach about assent to impressions?
We are constantly assailed by impressions from the outside world. The crucial point is that it is not the impression itself that troubles us, but our assent to it, our judgment about it. If an impression arises, do not say 'This is terrible!' Instead, ask, 'Is this impression something within my control?' If it is not, then it is merely an impression, and I need not assent to it as representing an inevitable reality.