ἃ πάσχοντες ὑφʹ ἑτέρων ὀργίζεσθε, ταῦτα τοὺς ἄλλους μὴ ποιεῖτε. - Isocrates

The greatest thing in the small compass is a sound mind in a human body. Strive with all your body to be a lover of toil, and with your soul to be a lover of wisdom, in order that with the one you may have the strength to carry out your resolves, and with the other the intelligence to foresee what is for your good.

With these examples before you, you should aspire to nobility of character, and not only abide by what I have said, but acquaint yourself with the best things in the poets as well, and learn from the other wise men also any useful lessons they have taught. For just as we see the bee settling on all the flowers, and sipping the best from each, so also those who aspire to culture ought not to leave anything untasted, but should gather useful knowledge from every source. For hardly even with these pains can they overcome the defects of nature.

Consider that nothing in human life is stable; for then you will not exult overmuch in prosperity, nor grieve overmuch in adversity. Rejoice over the good things which come to you, but grieve in moderation over the evils which befall you, and in either case do not expose your heart to others; for it were strange to hide away one's treasure in the house, and yet walk about laying bare one's feelings to the world.