Misfortune nobly born is good fortune.

From the philosopher Catulus, never to be dismissive of a friend's accusation, even if it seems unreasonable, but to make every effort to restore the relationship to its normal condition.

You have the power to strip away many superfluous troubles located wholly in your judgement, and to possess a large room for yourself embracing in thought the whole cosmos, to consider everlasting time, to think of the rapid change in the parts of each thing, of how short it is from birth until dissolution, and how the void before birth and that after dissolution are equally infinite.

You need to avoid certain things in your train of thought: everything random, everything irrelevant. And certainly everything self-important or malicious. You need to get used to winnowing your thoughts, so that if someone says, "What are your thinking about?" you can respond at once (and truthfully) that you are thinking this or thinking that.

No amount of misfortune will satisfy the man who is not satisfied with reading a hundred epigrams

If you are distressed by anything external, the pain is not due to the thing itself, but to your estimate of it; and this you have the power to revoke at any moment.