The universe is a shrine for the gods. (Cf. Plato, Timaeus 37c)

Plato emphasizes mathematics in his education of the upper classes, as described in the Republic. While mathematical knowledge has practical benefits, it is to be studied for its own sake, as it aids us in “knowing what always is, not what comes into being and passes away” (Republic 527b).

Be mathematically literate.

Men are disturbed, not by things, but by the principles and notions which they form concerning things. ... When therefore we are hindered, or disturbed, or grieved, let us never attribute it to others, but to ourselves; that is, to our own principles.

Epictetus, The Handbook, 5

The universe is always happy; and our soul will likewise be happy, when it is assimilated to the universe; for thus it will be led back to its cause. Hence, when the sensible man is assimilated to the universe, he also imitates his paradigm after an appropriate manner, becoming a world through similitude to the world, and happy through resemblance to that blessed God, the universe.

Proclus, Commentary on the Timaeus, Book I

Consider both the praise and the reproach of every foolish person as ridiculous, and the whole life of an ignorant man as a disgrace.

The Pythagoric Sentences of Demophilus

Don't be prideful with any excellence that is not your own. ... What, then, is your own? Only your reaction to the appearances of things. Thus, when you behave conformably to nature in reaction to how things appear, you will be proud with reason.

Epictetus, The Handbook, 6

In other words, be proud of how you respond, think, and act but not of, for example, the things you own.

In Platonism, the world is considered beautiful and as good as it possibly could be, despite its imperfections.

Indeed, to understand the cosmos is, in an important sense, to understand divinity. This is why the Greeks were lovers of mathematics and science.

At the same time, we are not to attach ourselves to the lower elements of physicality, and our passions and instincts should always be ruled over by discipline and wisdom.

Enjoy the world around you but always be prepared to give it and things in it up. (Cf. Epictetus, The Handbook, 7)

"The fully actualized soul, from a Platonic perspective, becomes a kind of cooperating junior partner, so to speak, with the gods in bringing order to the cosmos. And so when we bring order to our inner psychic cosmos, we are cooperating in the gods' own cosmogonic work. We're cooperating in that labor of demiurgy."

Edward Butler, https://youtu.be/cRU8Qh-kYhE

Don't demand that things happen as you wish, but wish that they happen as they do happen, and you will go on well.

Epictetus, The Handbook, 8

In modern times, a philosopher is some sterile academic. But a true philosopher, a philosopher in the Hellenic tradition, is much more like a sage or a Vedic rishi.

Sickness is a hindrance to the body, but not to your ability to choose, unless that is your choice. Lameness is a hindrance to the leg, but not to your ability to choose. Say this to yourself with regard to everything that happens, then you will see such obstacles as hindrances to something else, but not to yourself.

Epictetus, The Handbook, 9

With every accident, ask yourself what abilities you have for making a proper use of it. If you see an attractive person, you will find that self-restraint is the ability you have against your desire. If you are in pain, you will find fortitude. If you hear unpleasant language, you will find patience. And thus habituated, the appearances of things will not hurry you away along with them.

Epictetus, The Handbook, 10

"The soul reasons best when none of these senses troubles it, neither hearing nor sight, nor pain nor pleasure, but when it is most by itself, taking leave of the body and as far as possible having no contact or association with it in its search for reality."

Plato, Phaedo 65c

Never say of anything, "I have lost it"; but, "I have returned it." Is your child dead? It is returned. Is your wife dead? She is returned. Is your estate taken away? Well, and is not that likewise returned? "But he who took it away is a bad man." What difference is it to you who the giver assigns to take it back? While he gives it to you to possess, take care of it; but don't view it as your own, just as travelers view a hotel.

Epictetus, The Handbook, 11

In the intelligible [realm] we have real being which is stable and causal, eternal and true. In the material realm we have things which are constantly rising into existence but never really are; material things are effects of intelligible causes; they are temporal and in varying degrees deceptive unless their relation to real being, or ideas, is acknowledged. Much of the unspoken "philosophy" of our materialistic civilization implies that material things are real and abstract things are less real: this is a reversal of the true state of things according to the Platonic tradition.

Tim Addey, Beyond the Shadows

Begin therefore from little things. Is a little oil spilt? A little wine stolen? Say to yourself, "This is the price paid for equanimity, for tranquillity, and nothing is to be had for nothing."

Epictetus, The Handbook, 12

For all the Grecian theology is the progeny of the mystic tradition of Orpheus; Pythagoras first of all learning from Aglaophemus the orgies of the Gods, but Plato in the second place receiving an all-perfect science of the divinities from the Pythagoric and Orphic writings.

Proclus, On the Theology of Plato, Book I Chapter V

A basic prayer form with variations in detail arises from its function. At the beginning, underlined by the request 'Hear!', comes the name of the deity. Great importance is attached to finding the right name, especially appropriate epithets; as much as possible, epithets are heaped one upon another - a feature which probably also derives from Indo-European tradition - and the god is also offered the choice: 'With whatever name it pleases you to be called'. An attempt is also made to define the sphere of the god spatially by naming his favored dwelling place or several possible places from which he is to come. This is followed by a justification for calling on the god, in which earlier proofs of friendship are invoked by way of precedent: if ever the god has come to the aid of the suppliant, or if the suppliant has performed works pleasing to the god, has burned sacrifices and built temples, then this should now hold good. Often the assurance 'for you are able' is slipped in. Once contact has been established, the entreaty is made succinctly and clearly and is usually accompanied by the promise for the future, the vow; piety is supposed to guarantee constancy. Philosophically refined religious sensibility later took exception to the self-interested directness of the euchai; one should, it was recommended, pray simply for the Good and leave the decision to the god.

Walter Burkert, Greek Religion, II.3

A cult image or sanctuary must always be given a friendly greeting - a chaire - even if one is simply passing by without any special reason, or else the gesture of a kiss may be made by raising a hand to one's lips; a short, simple prayer may always be added.

Burkert, Greek Religion, II.3