In this type of action, we do not have total power, we are not only active cause and determining the success of our action. As a result, we are exposed to setbacks or disappointments that will make us unhappy.
To be free is to focus on the things that depend on us, and do not give importance to those that do not depend on us. Indeed, they do not depend on our own will, but the chance of external circumstances, for example, fame to which we aspire does not depend entirely on our talent, but also those who will come and bother discover this talent.
Like the Socrates of Plato's early dialogues, Epictetus does not impose elaborate doctrines on his audience. Rather, he exhorts them to try to know themselves, to practise self-examination, and to discover a source of goodness that is purely internal, independent of outward contingencies, yet capable of generating both personal happiness and integrity (p. 92).
What do we admire? Externals. About what things are we busy? Externals. And have we any doubt then why we fear or why we are anxious? What then happens when we think the things, which are coming on us, to be evils? It is not in our power not to be afraid, it is not in our power not to be anxious. Then we say, Lord God, how shall I not be anxious? Fool, have you not hands, did not God make them for you? Sit down now and pray that your nose may not run. Wipe yourself rather and do not blame him
OF INDIFFERENCE.—The hypothetical proposition is indifferent: the judgment about it is not indifferent, but it is either knowledge or opinion or error. Thus life is indifferent: the use is not indifferent. When any man then tells you that these things also are indifferent, do not become negligent; and when a man invites you to be careful (about such things), do not become abject and struck with admiration of material things.
The linchpin of Epictetus' entire philosophy is his account of what it is to be a human being; that is, to be a rational mortal creature. “Rational” as a descriptive term means that human beings have the capacity to “use impressions” in a reflective manner. Animals, like humans, use their impressions of the world in that their behavior is guided by what they perceive their circumstances to be. But human beings also examine the content of their impressions to determine whether they are true or false; we have the faculty of “assent” (1.6.12-22).
A Greek philosopher of 1st and early 2nd centuries C.E., and an exponent of Stoic ethics notable for the consistency and power of his ethical thought and for effective methods of teaching. Epictetus' chief concerns are with integrity, self-management, and personal freedom, which he advocates by demanding of his students a thorough examination of two central ideas, the capacity he terms ‘volition’ (prohairesis) and the correct use of impressions (chrēsis tōn phantasiōn). Heartfelt and satirical by turns, Epictetus has had significant influence on the popular moralistic tradition, but he is more than a moralizer; his lucid resystematization and challenging application of Stoic ethics qualify him as an important philosopher in his own right
Epictetus, (born ad 55, probably at Hierapolis, Phrygia [now Pamukkale, Turkey]—died c. 135, Nicopolis, Epirus [Greece]), Greek philosopher associated with the Stoics, remembered for the religious tone of his teachings, which commended him to numerous early Christian thinkers
It's not what happens to you, but how you react to it that matters.
“There is only one way to happiness and that is to cease worrying about things which are beyond the power of our will.”