The Greek word pathos (πάθος) is often translated as "emotion" in English, but the Greek word (at least in the context of Stoic philosophy) does not refer to everything the English word "emotion" denotes.

Different translators handle the poor match between Stoic technical jargon and modern English in different, contradictory ways. For example, some translators translate pathos as "emotion" and propathos as "feeling", while others (very confusingly) translate pathos as "passion" and propathos as "emotion" (or sometimes "pre-passion"). One way to avoid ambiguity is to think of them as "feeling" and "passion," and use "emotion" to mean either.

Passions (πάθοι) are emotions caused or reinforced by a belief something outside of one's control is good or bad. Feelings, on the other hand, are closer to perceptions we have, and not things either to be controlled or avoided; a Stoic "merely" should avoid being led by them to false beliefs about good and bad. The distinction is analogous to seeing an optical illusion, where "feeling" corresponds to "seeing" the illusion, while "passion" is corresponds to actually believing it. Marcus Aurelius expresses it like this (Meditations 5.25, Chrystal's translation):

Let the leading and ruling part of your soul stand unmoved by the stirrings of the flesh, whether gentle or rude. Let it not commingle with them, but keep itself apart, and confine these passions to their proper bodily parts; and if they rise into the soul by any sympathy with the body to which it is united, then we must not attempt to resist the sensation, seeing that it is of our nature; but let not the soul, for its part, add thereto the conception that the sensation is good or bad.

Unlike the full scope of what "emotions" and "feelings" refer to in English, πάθος/passions necessarily involve judgements and values: feelings that "rise into the soul by any sympathy with the body to which it is united" are not to be resisted. To be a passion, the rational mind needs to participate in the creation of the feeling: it needs to judge something good or bad. From Seneca's On Anger 2.3 (discussing the passion of anger specifically):

None of these things which casually influence the mind deserve to be called passions: the mind, if I may so express it, rather suffers passions to act upon itself than forms them. A passion, therefore, consists not in being affected by the sights which are presented to us, but in giving way to our feelings and following up these chance promptings: for whoever imagines that paleness, bursting into tears, lustful feelings, deep sighs, sudden flashes of the eyes, and so forth, are signs of passion and betray the state of the mind, is mistaken, and does not understand that these are merely impulses of the body. Consequently, the bravest of men often turns pale while he is putting on his armour; when the signal for battle is given, the knees of the boldest soldier shake for a moment; the heart even of a great general leaps into his mouth just before the lines clash together, and the hands and feet even of the most eloquent orator grow stiff and cold while he is preparing to begin his speech. Anger must not merely move, but break out of bounds, being an impulse: now, no impulse can take place without the consent of the mind: for it cannot be that we should deal with revenge and punishment without the mind being cognisant of them. A man may think himself injured, may wish to avenge his wrongs, and then may be persuaded by some reason or other to give up his intention and calm down: I do not call that anger, it is an emotion of the mind which is under the control of reason.

The practical dividing line between a passion and feeling, the question of which feelings are caused by judgements or prevent us from acting according to our best judgement, has been the subject of some debate. Some regard as "passions" only emotional problems of the sort one might see as requiring counselling for depression, anger management, or similar issues, while others see the majority of what a modern person thinks of as "emotions" as being passions, and that "feelings" are limited to emotions of the variety caused by reactions to music or fiction.

Even concerning emotions they considered pathological (passions), "repression" is not what the Stoics advocated, but rather extirpation. "Repressing" an emotion is somewhat analogous to getting a broken leg, but not treating it and attempting to walk on it normally, because that is what a healthy person would do. What the Stoics advocated was more analogous to healing the leg, and preventing it from being broken in the first place.

For a more extended discussion and related quotes and extracts from classical texts, see this /r/Stoicism wiki page. For a much more in-depth analysis and discussion of historical evidence, consult Margaret Graver's Stoicism and Emotion.

Does Stoicism encourage passively accepting your fate?

While the Stoics did advocate acceptance of all externals, "acceptance" seems to have been meant in the context of one's emotional reaction, rather than in actions to be taken, or not. It does not seem to imply passivity in action. Indeed, in Marcus Aurelius's Meditations, his exhortations of acceptance are often accompanied by exhortations to virtuous action. For example, see Meditations 9.6:

It is enough if your opinion in the present is based on understanding, your action in the present directed to the common good, and your disposition in the present one of contentment with all that befalls you from a cause outside yourself.

and 8.7:

Every nature is well content when its progress is good. And the progress of a rational creature is good when that nature yields to nothing false or obscure in thought, when it directs its impulses to social acts alone, and when its appetites and aversions are confined to what is within our power, and when it has a welcome for every dispensation of the universal Nature.

(Jackson translation, modernized)

The same themes are paired many other places; for much more discussion and many similar citations, see Hadot's The Inner Citadel.

The Meditations includes other exhortations to action and against passivity. Consider 9.16:

Not in passivity but activity lies the good of the rational and civic being, precisely as virtue and vice to the same lie in action not in passion.

and also 9.5:

Injustice lies as often in omission as commission.

What is important is to be a good person, to be virtuous, to show excellence of character. These are ἐφ' ἡμῖν (eph' hêmin), "in our control." What should be accepted are things not in your control, "all that befalls you from a cause outside yourself."

Consider the example of Priscus Helvidius from Epictetus's Discourses, book 1:

Priscus Helvidius also saw this, and acted conformably. For when Vespasian sent and commanded him not to go into the senate, he replied, "It is in your power not to allow me to be a member of the senate, but so long as I am, I must go in." "Well, go in then," says the emperor, "but say nothing." "Do not ask my opinion, and I will be silent." "But I must ask your opinion." "And I must say what I think right." "But if you do, I shall put you to death." "When then did I tell you that I am immortal? You will do your part, and I will do mine: it is your part to kill; it is mine to die, but not in fear: yours to banish me; mine to depart without sorrow."

In this example, we see Priscus Helvidius persistently acting as he thinks a virtuous person should act, without regard to the consequences for himself.

It should be remembered that Marcus Aurlius wrote his exhortations for himself alone, when he was already emperor. Stoic advice to others was not generally to be so selfless, or lacking in ambition; humility and selflessness were given much less emphasis in the Stoic conception of virtue than in the Christian.

From Cicero's On Duties 3.10, quoting Chrysippus:

And yet we are not required to sacrifice our own interest and surrender to others what we need for ourselves, but each one should consider his own interests, as far as he may without injury to his neighbour's. "When a man enters the foot- race," says Chrysippus with his usual aptness, "it is his duty to put forth all his strength and strive with all his might to win; but he ought never with his foot to trip, or with his hand to foul a competitor. Thus in the stadium of life, it is not unfair for anyone to seek to obtain what is needful for his own advantage, but he has no right to wrest it from his neighbour."

... although everyone did have social responsibilities: from Cicero's On Duties 3.5:

Well then, for a man to take something from his neighbour and to profit by his neighbour's loss is more contrary to Nature than is death or poverty or pain or anything else that can affect either our person or our property. For, in the first place, injustice is fatal to social life and fellowship between man and man. For, if we are so disposed that each, to gain some personal profit, will defraud or injure his neighbour, then those bonds of human society, which are most in accord with Nature's laws, must of necessity be broken. Suppose, by way of comparison, that each one of our bodily members should conceive this idea and imagine that it could be strong and well if it should draw off to itself the health and strength of its neighbouring member, the whole body would necessarily be enfeebled and die; so, if each one of us should seize upon the property of his neighbours and take from each whatever he could appropriate to his own use, the bonds of human society must inevitably be annihilated. For, without any conflict with Nature's laws, it is granted that everybody may prefer to secure for himself rather than for his neighbour what is essential for the conduct of life; but Nature's laws do forbid us to increase our means, wealth, and resources by despoiling others.

A failure of ambition can even be seen as being disgraceful, and a vice. From On Duties 1.71: