Epictetus Discourses 3.2 - What a person must train himself in if he is to make progress, and that we neglect what is most important

The fields of study in which the man who expects to make progress will have to go into training; and that we neglect what is most important

Below are the first few verses of chapter 2 from book 3.  I've formatted it slightly differently.

"There are three areas of study in which someone who wants to be virtuous and good must be trained:

1. that which relates to desires and aversions, so that he may neither fail to get what he desires, nor fall into what he wants to avoid;
2. that which relates to our motives to act or not to act, and, in general, appropriate behaviour, so that he may act in an orderly manner and with good reason, rather than carelessly;
3. and thirdly, that which relates to the avoidance of error and hasty judgement, and, in general, whatever relates to assent.

"Of these, the most important and most urgent is that which is concerned with the passions, for these arise in no other way than through our being frustrated in our desires and falling into what we want to avoid. This is what brings about disturbances, confusions, misfortunes, and calamities, and causes sorrow, lamentation, and envy, making people envious and jealous, with the result that we become incapable of listening to reason.

"The second is concerned with appropriate action; for I shouldn’t be unfeeling like a statue, but should preserve my natural and acquired relationships, as one who honours the gods, as a son, as a brother, as a father, as a citizen.

"The third belongs to those who are already making progress, and is concerned with the achievement of constancy in the matters already covered, so that even when we’re asleep, or drunk, or depressed, no untested impression that presents itself may catch us off guard."

Furthermore, you know you are making progress when a "bit of money is involved" and you can avoid the deception of it making you happy.  Or when "you see a pretty girl" and you can "resist the impression" she bears on your mind.  Or when your "neighbor receives an inheritance" and you don't feel the bite of envy.  Or when you lack nothing but "unshakable judgement" (see v. 7-8, p. 148).

Further along, he offers this insightful thought; "when one has shown what his judgements are, then one has shown what he is as a human being" (v. 12, p. 148).

And some parting advice:

"Put aside these things that don't concern you"

Don't give in to "anger, distress or envy; [be] free from hindrance and constraint"