Chapter 2 of the manual of Epictetus

Remember that your desires command you to strive for what you desire and that your fears command you to avoid what you dislike. Those who fail to get what they desire feel bad, and those who fail to avoid what they fear feel miserable. If you limit yourself to striving for the natural things that you control, you will never feel miserable; but if you try to avoid illness, death and poverty, you will experience setbacks.
Therefore you have to stop completely to strive for things that you do not have control over. Just focus your attention on the things in your power. For the time being completely stop to strive for anything. If you accidentally strive for one of the things that are not in your power, you will eventually fail and feel rotten. None of those things that are in your power, are within your grasp yet. Limit yourself for the time being only to your impulses to do something or not, but do so in moderation and with reserve and control.

In this chapter Epictetus tells us that we cannot avoid feeling miserable if we continue to strive to obtain and avoid things that are not fully in our control. The only thing that helps against these unpleasant emotions is letting go of your desires and forsaking your fears. He who gives up all hope regains his freedom and peace of mind.

At first sight that appears contrary to human nature and even totally impossible. Yet that is precisely what stoic philosophy focuses on. Luckily Epictetus does not stop here, he offers his students a whole range of exercises and techniques with which they can learn to keep their desires and fears in check. Letting go of your desires and fears is called the 'doctrine (or topos in Greek) of the right will'. This 'doctrine of the right will' is one of the three learning objectives of the stoic curriculum, in addition to 'the doctrine of correct judgment' and 'the doctrine of right action'. This is not surprising if you consider that the frustration of your desires and the assertion of your fears usually give rise to a whole series of unpleasant emotions. You feel angry, disappointed and frightened when you are thwarted in your efforts. Epictetus tells us that in the end it is inevitably to be thwarted anyway. You will not always be able to get what you want and you will not always be able to avoid what you are afraid of. Setbacks are inevitable, but the feelings that this evokes in you are not.

Epictetus wants his students to completely abandon the pursuit of things they desire or the avoidance of things they fear for the time being. In fact, they should only occupy themselves with the things over which they have total control. In that case it is impossible to fail, you always have the ability to succeed in what you want. He means desires and aversions, judgments and impulses to act. But even these things, students can at first better abandon. They do not know well enough the difference between the things you control and the things that are beyond your control. As long as they have not fully mastered this difference, they have to limit themselves to their natural impulses. But what are those natural impulses?

According to the Stoics all animals, and therefore also all humans, are driven by certain natural impulses. It is similar to what we call instincts. If you walk thirsty through the desert and see a pool of water, you get the impulse to drink water from that pool. The Stoics say that you get the impression of a pool of water from the outside world. That impression gives you the impulse to start drinking, because you are thirsty. If you are not the only thirsty person at the pool and you get the impression of an evil lion storming at you, then you might get the impulse to climb one of the nearby palm trees. Impulses or instincts thus determine the survival behaviour of most living beings.

Epictetus advises his pupils to be for the time being guided by these natural instincts. But everything in moderation. After all, it is not the intention that a student of stoicism who sees a beautiful lady or gentleman pass by will immediately be entrained by his sexual impulses and will throw himself or herself on him or her.