Observe constantly that all things take place by change.

Even while a thing is in the act of coming into existence, some part of it has already ceased to be.

For nowhere either with more quiet or more freedom from trouble does a man retire than into his own soul, particularly when he has within him such thoughts that by looking into them he is immediately in perfect tranquility; and I affirm that tranquility is nothing else than the good ordering of the mind.

If you are pained by any external thing, it is not this that disturbs you, but your own judgment about it.

If this is neither my own badness, nor an effect of my own badness, and the common weal is not injured, why am I troubled about it? And what is the harm to the common weal?

Frequently consider the connection of all things in the universe.

Think of yourself as dead. You have lived your life. Now, take what's left and live it properly. What doesn't transmit light creates its own darkness.