You may judge it the most grievous of ills to lose any of those you love; while all the same this would be no less foolish than weeping because the trees which charm your eye and adorn your home lose their foliage.
Regard everything that pleases you as if it were a flourishing plant; make the most of it while it is in leaf, for different plants at different seasons must fall and die. But just as the loss of leaves is a light thing, because they are born afresh, so it is with the loss of those whom you love and regard as the delight of your life; for they can be replaced even though they cannot be born afresh.

“New friends, however, will not be the same.” No, nor will you yourself remain the same; you change with every day and every hour. But in other men you more readily see what time plunders; in your own case the change is hidden, because it will not take place visibly. Others are snatched from sight; we ourselves are being stealthily filched away from ourselves.
You will not think about any of these problems, nor will you apply remedies to these wounds. You will of your own volition be sowing a crop of trouble by alternate hoping and despairing. If you are wise, mingle these two elements: do not hope without despair, or despair without hope.

~ Seneca, On Care of Health and Peace of Mind

Around 50 AD, the major philosophical schools were the following:

• Stoic: They claimed that the only true good is virtue, while everything else is indifferent. However, some things are preferable to others—for example, good health is not inherently good but is preferable to sickness.
  • Followers: Zeno, Chrysippus, Epictetus, Seneca, Marcus Aurelius
• Cynic: This school can be seen as a more extreme version of Stoicism. Virtue is still considered the only good, but Cynics also reject all wealth, power, glory, and worldly possessions.
  • Followers: Diogenes
• Epicurean: They were hedonists, valuing pleasure as the highest good. However, they claimed that the highest pleasure is achieved through a simple life and abstinence.
  • Followers: Epicurus
• Peripatetic: This school can be interpreted as a weaker form of Stoicism. Virtue is still considered the highest good, but things like wealth and good health are also regarded as good.
  • Followers: Aristotle
• Academic Skepticism: They believed that knowledge of any kind is impossible—for example, we cannot be certain that external objects exist.
  • Followers: Arcesilaus, Carneades, Cicero
• Skepticism/Pyrrhonism: They rejected all dogma, claiming that we should suspend all judgment because we can never be certain of knowing anything. Importantly, they did not claim that knowledge is impossible—only that we cannot be sure.
  • Followers: Pyrrho, Aenesidemus

Do you forbid me to have a share in heaven? In other words, do you bid me live with my head bowed down? No, I am above such an existence; I was born to a greater destiny than to be a mere chattel of my body, and I regard this body as nothing but a chain which manacles my freedom. Therefore, I offer it as a sort of buffer to fortune, and shall allow no wound to penetrate through to my soul.

For my body is the only part of me which can suffer injury. In this dwelling, which is exposed to peril, my soul lives free. Never shall this flesh drive me to feel fear or to assume any pretence that is unworthy of a good man. Never shall I lie in order to honour this petty body. When it seems proper, I shall sever my connexion with it. And at present, while we are bound together, our alliance shall nevertheless not be one of equality; the soul shall bring all quarrels before its own tribunal. To despise our bodies is sure freedom

~ Seneca, On the First Cause