Besides, if a man is afraid of pain, he is afraid of something happening which will be part of the appointed order of things, and this is itself a sin; if he is bent on the pursuit of pleasure, he will not stop at acts of injustice, which again is manifestly sinful. No; when Nature herself makes no distinction — and if she did, she would not have brought pains and pleasures into existence side by side — it behooves those who would follow in her footsteps to be like-minded and exhibit the same indifference.

[ἔτι δὲ ὁ φοβούμενος τοὺς πόνους φοβηθήσεταί ποτε καὶ τῶν ἐσομένων τι ἐν τῷ κόσμῳ, τοῦτο δὲ ἤδη ἀσεβές: ὅ τε διώκων τὰς ἡδονὰς οὐκ ἀφέξεται τοῦ ἀδικεῖν, τοῦτο δὲ ἐναργῶς ἀσεβές: χρὴ δὲ πρὸς ἃ ἡ κοινὴ φύσις ἐπίσης ἔχει ῾οὐ γὰρ ἀμφότερα ἃν ἐποίει, εἰ μὴ πρὸς ἀμφότερα ἐπίσης εἶχἐ, πρὸς ταῦτα καὶ τοὺς τῇ φύσει βουλομένους ἕπεσθαι, ὁμογνώμονας ὄντας, ἐπίσης διακεῖσθαι.]

Marcus Aurelius (AD 121-180) Roman emperor (161-180), Stoic philosopher

Meditations [To Himself; Τὰ εἰς ἑαυτόν], Book 9, ch. 1 (9.1) (AD 161-180) [tr. Staniforth (1964)]
    (Source)

(Source (Greek)). Alternate translations:

Again, he that feareth pains and crosses in this world, feareth some of those things which some time or other must needs happen in the world. And that we have already showed to be impious. And he that pursueth after pleasures, will not spare, to compass his desires, to do that which is unjust, and that is manifestly impious. Now those things which unto nature are equally indifferent (for she had not created both, both pain and pleasure, if both had not been unto her equally indifferent): they that will live according to nature, must in those things (as being of the same mind and disposition that she is) be as equally indifferent.
[tr. Casaubon (1634)]

To go on: He that's afraid of Pain, or Affliction; will be afraid of something that will always be in the World; but to be thus uneasie at the Appointments of Providence, is a failure in Reverence, and Respect. On the other hand; He that's violent in the pursuit of Pleasure, won't stick to turn Villain for the Purchase: And is not this plainly , an Ungracious, and an Ungodly Humour? To set the Matter Right, where the Allowance of God is equally clear; as it is with Regard to Prosperity, and Adversity: For had he not approved both these Conditions, He would never have made them: I say where the Good Liking of Heaven is equally clear, Ours ought to be so too: Because we ought to follow the Guidance of Nature, and the Sense of the Deity.
[tr. Collier (1701)]

Besides, he who dreads pain, must sometimes dread that which must be a part of the order and beauty of the universe: this, now, is impious: and, then, he who pursues pleasures will not abstain from injury; and that is manifestly impious. But, in those things to which the common nature is indifferent, (for she had not made both, were she not indifferent to either); he who would follow nature, ought, in this too, to agree with her in his sentiments, and be indifferently dispos'd to either.
[tr. Hutcheson/Moor (1742)]

Nay, he that is uneasy under affliction, is uneasy at what must necessarily exist in the world. This uneasiness, then, is a degree of impiety: and he who is too eager in his pursuit of pleasures, will not abstain from injustice to procure them. This is manifestly impious.
In short, as nature herself seems to view with indifference prosperity and adversity, (as she certainly does, or she would not produce them) so he who would follow nature as his guide, ought to do the same.
[tr. Graves (1792)]

And further, he who is afraid of pain will sometimes also be afraid of some of the things which will happen in the world, and even this is impiety. And he who pursues pleasure will not abstain from injustice, and this is plainly impiety. Now with respect to the things towards which the universal nature is equally affected -- for it would not have made both, unless it was equally affected towards both -- towards these they who wish to follow nature should be of the same mind with it, and equally affected.
[tr. Long (1862)]

Now, he that is afraid of pain will be afraid of something that will always be in the world; but this is a failure in reverence and respect. On the other hand, he that is violent in the pursuit of pleasure, will not hesitate to turn villain for the purchase. And is not this plainly an ungodly act? to set the matter right, where the allowance of God is equally clear, as it is with regard to prosperity and adversity (for had He not approved both of these conditions, He would never have made them both), I say, where the good liking of heaven is equally clear, ours ought to be so too, because we ought to follow the guidance of nature and the sense of the Deity.
[tr. Collier/Zimmern (1887)]

Moreover, he who fears pain will some time fear that which will form part of the world-order; and therein he sins. And he who seeks after pleasures will not abstain from unjust doing; which is palpably an act of sin. Where Nature makes no difference -- and were she not indifferent, she would not bring both to pass -- those who would fain walk with Nature should conform their wills to like indifference.
[tr. Rendall (1898)]

Again, he who dreads pain must sometimes dread a thing which will make part of the world order, and this is impious. And he who pursues pleasure will not abstain from injustice, and this is clear impiety. In those things to which the common nature is indifferent (for she had not made both, were she not indifferent to either), he who would follow Nature ought, in this also, to be of like mind with her, and shew the like indifference.
[tr. Hutcheson/Chrystal (1902)]

Moreover he that dreads pain will some day be in dread of something that must be in the world. And there we have impiety at once. And he that hunts after pleasures will not hold his hand from injustice. And this is palpable impiety.
But those, who are of one mind with Nature and would walk in her ways, must hold a neutral attitude towards those things towards which the Universal Nature is neutral—for she would not be the Maker of both were she not neutral towards both.
[tr. Haines (Loeb) (1916)]

He who fears pains will sometimes fear what is to come to pass in the Universe, and this is at once sinful, while he who pursues pleasures will not abstain from doing injustice, and this is plainly sinful. But those who wish to follow Nature, being like-minded with her, must be indifferent towards the things to which she is indifferent, for she would not create both were she not indifferent towards both.
[tr. Farquharson (1944)]

And furthermore, one who is afraid of pain is sure to be afraid at times of things which come to pass in the universe, and that is already an impiety; and one that pursues pleasure will not abstain from injustice, and that is manifest impiety. But towards those things with regard to which universal nature is neutral (for she would not have created both opposites unless she was neutral with regard to both), it is necessary that those who wish to follow nature and be of one mind with her should also adopt a neutral attitude.
[tr. Hard (1997 ed.)]

And moreover, to fear pain is to fear something that’s bound to happen, the world being what it is -- and that again is blasphemy. While if you pursue pleasure, you can hardly avoid wrongdoing -- which is manifestly blasphemous.
Some things nature is indifferent to; if it privileged one over the other it would hardly have created both. And if we want to follow nature, to be of one mind with it, we need to share its indifference.
[tr. Hays (2003)]

Further, anyone who fears pain will also at times be afraid of some future event in the world, and that is immediate sin. And a man who pursues pleasure will not hold back from injustice -- an obvious sin. Those who wish to follow Nature and share her mind must themselves be indifferent to those pairs of opposites to which universal Nature is indifferent -- she would not create these opposites if she were not indifferent either way.
[tr. Hammond (2006)]

And furthermore, one who is afraid of pain is sure to be afraid at times of things which come about in the universe, and that is already an impiety; and one who pursues pleasure will not abstain from injustice, and that is a manifest impiety. But towards those things with regard to which universal nature is neutral (for she would not have created both opposites unless she was neutral with regard to both), it is necessary that those who wish to follow nature and be of one mind with her should also adopt a neutral attitude.
[tr. Hard (2011 ed.)]